Question about 1999 Oldsmobile Alero

1 Answer

Electric fuel pump for 90 cherokee won't work properly.

The pump and the relay are new. The ignition switch is good. The battery is good. Continuity from hot to ground is good on both the line and the load side of the power connection to the pump. A nightmare to get the thing started. Once it has been running, it can be shut off, and then right back on again, but only if it does not sit for more than a minute or so. I've had some good suggestions.. but haven't been able to solve the problem. Will greatly appreciate any help or advise. It's a 4.0 liter MPI. Thanx-a-bunch.

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  • 11 more comments 
  • graywolf0577 May 10, 2009

    Thanx for the tip. The pressure regulator is good. Any other suggestions???

  • graywolf0577 May 10, 2009

    Runs a little rough at idle.. but smooth as butter when you throttle it up. No black smoke at all.

  • graywolf0577 May 10, 2009

    Thanx. It'll probably be tomorrow before I have any more questions. Thanx again for the tips.

  • graywolf0577 May 10, 2009

    Forgot to mention that I changed the plugs a week or so ago, and don't remember them being wet with fuel. I do have a pressure tester, but the connectors don't fit the fuel rail. The problem seems to revolve around the fuel pump not turning on when it is suppose to. I've written a novel on all of the different things that I have tried and tested under a different posting on this web page, but I don't if that info is available to you or not. I originally posted my problem back in April under the same screen name. If you still don't mind helping, and you can't find the other posting , let me know and I will re-write everything on this one. Thanx again.

  • graywolf0577 May 10, 2009

    It's posted by graywolf0577 on April 19, under "Electric fuel pump for 1990 Cherokee...". You'll know it if you find it, like I said it's practically a short novel. There's also one solution posted by "thundergod". Like I mention in my second comment under that posting, I hope I don't offend anyone by seeking different point of view. Thanx again for your time... it's greatly appreciated.

  • graywolf0577 May 10, 2009

    I have a second posting under "grounding connection for electric fuel pump on 1990 cherokee...", but that's not the one with all the details. They are both posted under "1990 Cherokee Limited". I think that's main chat forum or whatever it's called.

  • graywolf0577 May 10, 2009

    I figured I'd save you the trouble of trying to find the original posting as you are already being kind enough to help me out. If you're still there you might want to grab a seat 'cause this kind of long. This is what I originally posted: "Approximately 260,000 miles on vehicle. The pump is new. Second one that's been installed since the 230,000 mile mark. Fuel pump relay is good. Battery is new. Vehicle runs fine once the pump comes on, but requires excessive attempts to start when attempting a cold start. The vehicle can be turned off, and then restarted as long as it does not stay turned off for more than a few minutes. The entire electrical system energizes when you turn the key to the "run" position, but the fuel pump does not turn on. During the cold start, when the pump finally does turn on, I sometimes have to hold the throttle a little open to keep it from stalling until it has been running for a minute, and other times it will idle to high ( between 2000-3000 rpm's ), but not all of the time. I'm pretty sure that all of the electrical & vacuum connections are good, but I don't know, I'm not a mechanic, I've only checked what's easily accessible. I can fix it if I can find the cause of the problem. Again, it's a '90 Cherokee/ 4.0 liter/ MPI fuel injected inline-6, 5-speed manual, 4-wheel drive.
    The solution that was offered by another expert was: " A delay in fuel pump may be due to either a "lazy" relay or an insufficient ground ( fender, firewall, or pump itself ) It could be a poor connection at the ignition switch. However I took a look at the wiring diagram I have and it seems that there are several items connected to the power supply for the pump, which I see no real reason for being on that circuit at all. Have you tried a code check? Only other thing I can think of would be the anti-drainback valve in the pump, but the pump should come on and re-pressurize the system, not fail to run, even if the valve was bad. "
    I have part 2 of my novel to add to this... but I think my e-mail mght be recieving a reply... so I'll be right back.


  • graywolf0577 May 10, 2009

    Thanx. I've lost track of what info I've given you while I've been jumping back and forth between postings, so I'm going sign off for a minute or two and get my bearings. I entered a reply to your relay question on the other posting. Sorry about all of the confusion. I'm kind of a computer-dummy. Be back in a few.

  • graywolf0577 May 10, 2009

    Oh yeah... you can here the relay click after the ignition switch has been turned to "run". It clicks after about two seconds.

  • graywolf0577 May 11, 2009

    Thanx. If I remember correctly, there are only three wires going back to the pump. two colored and one black. I'm going to go and dig around in the tool box and see if I can find a test light, and then proceed with testing. It might be a little while before I sign back in. I really appreciate all of your help. I'm broke-as-a-joke and can't afford to pay someone, so your help has been a blessing. I'll post more feedback as soon as I can. Thanx again.

  • graywolf0577 May 11, 2009

    Hi again. The test light that I have is a clamp type and won't fit into the plastic wire connector. But I did get some readings with the multimeter that might be of value. On the line side of the connector there are three wires. A larger red with a black stripe, a smaller peach colored one, and a black that is the same size as the peach one. The reading for the red w/stripe to black 9.4 ohms of resistance with the circuit off, and reads a good 12.5 volts when you turn the circuit on. The reading for the smaller peach colored wire to black is 88.1 ohms of resistance with the circuit off, and 6.8 volts with the circuit on. Again... this is on the line side of the plastic connector. On the pump side of the connector there are also three wires. Purple, orange and black. All of these are the same size as the larger red with black stripe wire on the line side. On the pump side the readings are as follows: purple to black is 49.5 ohms of resistance, and orange to black is 1.1 ohm of resistance. When you plug the line side of the connector into the other connector on the pump side the wires connect as follows: red with stripe to orange. Purple to peach. And black to black. Look forward to more feed-back. Thanx again for everything.

  • graywolf0577 May 11, 2009

    P.S. I don't know if I'm chatting with "mechanicm 639" or "thundergod" as I've been jumping back and forth between the two postings.

  • graywolf0577 May 11, 2009

    Thanx. I'll leave you alone for the evening... I won't be able to do anymore testing tonight anyway since it's dark outside. I'll try to post some more feed-back tomorrow. You've been a huge help.

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  • 253 Answers

Check your fuel pressure regulator. It will have a vaccuum line to it. With the truck running pull the vac line and see if fuel comes out, if so it is bad and should be replaced. Good Luck

Posted on May 09, 2009

  • 6 more comments 
  • Mike White
    Mike White May 10, 2009

    It the truck running rough, or does it blow black smoke when it starts?

  • Mike White
    Mike White May 10, 2009

    I would let it sit for a little while, pull the plugs and see if any are wet with fuel. This can cause a hard start. If you have a fuel pressure gauge, connect it and after you kill the engine watch the gauge for a rapid fall in pressure. A slow drop is normal but rapid loss of pressure means you have some type of leak. The next time it fails to start try cycling the key off/on several times before you start it to see what happens. If you have a wet plug then you have a leaking injector. Let me know if I can help.

  • Mike White
    Mike White May 10, 2009

    Any time, glad to help

  • Mike White
    Mike White May 10, 2009

    I will see if I can find your post.

  • Mike White
    Mike White May 10, 2009

    The anti drain back (foot valve ) in the pump is why I was interested in the rapid pressure loss. Also having to hold your foot on the gas to get it to start may be a sign of a sticking injector, which would leave a plug wet and cause a rough idle for a moment or two. It sounds like you have the bases covered pretty good. When it fails to start can you hear the relay click? Have someone try to start it next time it fails and see if it clicks. The PCM provides a ground to the relay to make the contacts in the relay close completing the circuit for the pump. On the fuel pump connector you should have 4 wires. 2 grounds 1 wire for the gauge and a hot for the pump.The relay should have 1 hot at all times, 1 switched hot, a ground and a PCM controled ground. The PCM will send the ground to the relay while you are cranking the ignition and after it senses the vehicle is running through ignition inputs. If you have a bad foot valve you should be able to cycle the key on/off several times to get it to start. If your PCM is having some type of failure it should show up while checking the relay ground provided by the PCM. I will try to find more info for you. Thanks, Mike.

  • Mike White
    Mike White May 10, 2009

    Ok at the fuel pump connector, there will be 2 grounds, 1 wire that feeds the pump, and 1 wire for the gauge. The wire for the gauge is os a variable resistor. It will light a test light either dim, or will make it pulse. If both grounds are good, an ohm reading of less than 1 ohm, test the 12 volt supply for the pump at the pump connector. If when the vehicle fails to start you have a full 12 volts then your issue will be with the pump, or the connection inside the tank to the pump. You can test this at the harness close to the tank if you know what color wirefeeds the pump. Be sure to test all 12 volt positive circuits with a test light, because a volt meter will not (load) a circuit enough to really test it. Let me know if any of this helps.

  • Mike White
    Mike White May 11, 2009

    Ok the large red will be the pump feed, the peach is the gauge and black is ground.. The ground shouls be less than 1 ohm. The other readings are ok. I would take a jumper from your ground and hook it to a clean spot on the frame. Hook it up and see what happens. A high resistance in a ground can do some wierd things. If you do not have any luck let me know. You can tie the jumper wire in anywhere in the harness but try to get close to the connector, and to a bolt or screw in the frame.

  • Mike White
    Mike White May 11, 2009

    you have mechanicm, glad to help

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Auto shut down fuse blows when I start the truck?


This information is straight out of the 1997 Breeze/Stratus/Cirrus Factory Service Manual (Yes I paid the $90 for it years ago)

__________________________________________________ _______________

Automatic Shutdown (ASD) sense - PCM Input

The ASD sense circuit informs the PCM when the ASD relay energizes. A 12 volt signal at this input indicated to the PCM that the ASD has been activated. This input is used only to sense that the ASD relay is energized.
When energized, the ASD relay supplies battery voltage to the fuel injectors, ignition coils, and the heating element in each oxygen sensor. If the PCM does not receive 12 volts from this input after grounding the ASD reley, it sets a Diagnostic Trouble Code (DTC).

Automatic Shutdown Relay - PCM Output

The PCM operates the Automatic Shutdown (ASD) relay and fuel pump relay through one ground path. The PCM operates them by switching the ground path for the solenoid side of the realys on and off. Both realys turn on and off at the same time.
The ASD relay connects battery voltage to the fuel injectors and ignition coil. The fuel pump relay connects battery voltage to the fuel pump.
A buss bar in the power distribution center (PDC) supplies voltage to the solenoid side and contact side of the relay. The ASD relay power circuit contains a 20 amp fuse between the buss bar in the PDC and teh relay. The fuse also protects the power circuit for the fuel pump relay and pump. The fuse is located in teh PDC.
The PCM controls the relay by switching the ground path for the solenoid side of the relay on and off. The PCM turns the ground path off when the ignition switch is in the Off position. When the ignition switch is in the On or Crank position, the PCM monitors the crankshaft position sensor and the camshaft position sensor signals to determine engine speed and ignition timing (coil dwell). If the PCM does not receive the crankshaft position sensor and camshaft position when the ignition switch is in teh Run position, it will de-energize teh ASD relay.
The ASD relay and fuel pump relay are located in the PDC near the battery. The inside top of the PCD cover has a label showing relay and fuse location.

ASD and Fuel Pump Relays

The following description of operation and tests apply only to the Automatic Shutdown (ASD) and fuel pump relays. The terminals on the bottom of each relay are numbered.

'------------------'
' __85 ___________'
' __87A '87 '30 ___' Sorry for the crudeness of this. This is supposed to
' __86 ___________' be the relay terminals!
'------------------'

OPERATION
- Terminal number 30 is connected to battery voltage. For both the ASD and fuel pump relays, terminal 30 is connected to battery voltage at all times.
- The PCM grounds the coil side of the relay through terminal number 85.
- Terminal number 86 supplies voltage to the coil side of the relay.
- When the PCM de-energizes the ASD and fuel pump relays, terminal number 87A connects to terminal 30. This is the Off position. In the off position, voltage is not supplied to the rest of the circuit. Terminal 87A is the center terminal on the relay.
- When the PCM energizes the ASD and fuel pump relays, terminal 87 connects to terminal 30. This is the On position. Terminal 87 supplies voltage to the rest of the curcuit.

TESTING
The following procedure applies to the ASD and fuel pump relays.
(1) Remove relay from connector before testing.
(2) With the relay removed from the vehicle, use an ohmmeter to check the resistance between terminals 85 and 86. The resistance shoud be 75±5 ohms.
(3) Connect the ohmmeter between terminals 30 and 87A. The ohmmeter should show continuity between terminals 30 and 87A.
(4) Connect the ohmmeter between between terminals 87 and 30. The ohmmeter should not show continuity at this time.
(5) Connect one end of a jumper wire (16 guage or smaller) to relay terminal 85. Connect the other end of the jumper wire to the ground side of a 12 volt power source.
(6) Connect on end of another jumper wire (16 guage or smaller) to the power side of the 12 volt power source. Do not attach the other end of the jumper wire to the relay at this time.

WARNING: DO NOT ALLOW OHMMETER TO CONTACT TERMINALS 85 OR 86 DURING THIS TEST.

(7) Attach the other end of the jumper wire to relay terminal 86. This activates the relay. The ohmmeter should now show continuity between relay terminals 87 and 30. The ohmmeter should not show continuity between relay terminals 87A and 30.
(8) Disconnect jumper wires.
(9) Replace the relay if it did not pass the continuity and resistance tests. If the relay passed the tests, is operates properly. Check the remainder of the ASD and fuel pump curcuits.

__________________________________________________ _______________

I know you said you replaced the relay, and this is a test procedure for the relay, but I have bought bad parts in the past. The description before the test procedure at least gives you an idea of what components are wired through and controlled by the relay. One of those may be faulty. Email me if you want or need wiring diagrams and I should be able to scan them and email them to you.

Jul 15, 2015 | 1992 Dodge Dakota

2 Answers

Could I run a electric fuel pump on my 1998 Cadillac deville?


if it did not have an electric fuel before then the installation of an electric pump is a relatively easy process. If you have an electric pump already fitted but it has failed then remove it and install the new pump in its place. Take care to check all wires, fuses and relays and any pressure sensors for correct operation. Remove and blank of the opening for any mechanical pump on the engine
For new installation select an easily accessible place under the vehicle that can be protected from flying rocks and road debris. Run a power wire (red colour) from the run side of the ignition switch to the relay ( to be fitted ) near the battery or in the engine bay. Run this wire through an inline fuse close to the ignition switch to protect the circuit. attach to a coil actuation terminal of the relay.( look at the base of the relay for terminal identification. Run a black wire from the other side of the coil actuation pin on the relay to earth. Normally the same bolt that mounts the relay. Run a red wire capable of carrying 20 amps directly from the battery terminal through an inline fuse ( close to the terminal) to a power pin on the relay. Run another red wire from the outlet power pin on the relay to the electric pump. . Run an earth wire from the pump to earth.
This is a basic electric circuit for the installation of the pump. If there is a requirement for a pressure regulator or pressure sensor to control the pressure or pump operation , that control wire will be connected in series into the wire from the ignition switch so that when the pressure is reached then it breaks the circuit to the relay from the ign. switch and the pump will stop operation until the circuit is again completed. When the ignition switch is off there will be no power for the pump

Oct 09, 2014 | 1998 Cadillac DeVille

1 Answer

My 97 grand cherokee cranks but wont start any ideas


Check fuel pressure. If ok then go to ignition. If low fuel pressure, then its either:
  • Fuel filter
  • Fuel pump relay
  • Fuel pump
Ignition:

  1. Coil
  2. Ignition module
  3. dist. cap and rotor button if equipped. (give a good tuneup)
90% sure its fuel related

Dec 09, 2013 | 1997 Jeep Grand Cherokee

1 Answer

I have a 1996 Acura 3.5 R.L. just put a new fuel pump in and it won't start. It turns over, but will not stay started.


Check your main fuel relay.



Fuel Supply System


PGM-FI Main Relay


Description


This PGM-FI main relay is located behind the dashboard


lower cover. The PGM-FI main relay actually contains


two individual relays. One relay is energized whenever


the ignition is on. It supplies battery voltage to the PCM,


power to the fuel injectors, and power for the second


relay. The second relay is energized for 2 seconds when


the ignition is switched on, and when the engine is running.


It supplies power to the fuel pump.


PGM-FI


MAIN RELAY



FUEL


PUMP


RELAY


Relay Testing


NOTE: If the engine starts and continues to run, the PGMFI


main relay is OK.


1. Remove the PGM-FI main relay.


2. Attach the battery positive terminal to the No. 3*


terminal and the battery negative terminal to the


No. 2* terminal of the PGM-FI main relay. Then


check for continuity between the No. 5* terminal and


No. 2 terminal of the PGM-FI main relay.


• If there is continuity, go on to step 3.


• If there is no continuity, replace the relay and


retest.



*: 8P CONNECTOR


To FUEL PUMP


3. Attach the battery positive terminal to the No. 4 terminal


and the battery negative terminal to the No.


7* terminal of the PGM-FI main relay. Then check


that there is continuity between the No. 3 terminal


and No. 1 terminal of the PGM-FI main relay.


• If there is continuity, go on to step 4.


• If there is no continuity, replace the relay and


retest.


4. Attach the battery positive terminal to the No. 1 terminal


and battery negative terminal to the No. 2*


terminal of the PGM-FI main relay. Then check that


there is continuity between the No. 5* terminal and


No. 2 terminal of the PGM-FI main relay.


• If there is continuity, the relay is OK;


If the fuel pump still does not work, go to Harness


Testing on the next page.


• If there is no continuity, replace the relay and


retest.



To PCM CONNECTOR


TERMINAL A4


To ST. SWITCH


To GROUND


To IGN. 1 To BAT


To PCM


CONNECTOR TERMINALS


A13 and B1


FUEL PUMP


RESISTOR


FUEL PUMP

Sep 18, 2013 | 1996 Acura TL Series

1 Answer

My 99 s10 has no check engine light even when just turning the key, won't start and the fuel pump wont turn on. Changed ECM, Body control module, and ignition switch. I have checked all Fuses and...


IF FUEL PUMP RELAY IS NOT WORKING THE COMPUTER IS NOT READDING IT THEIR IS NO BYPASSING THE COMPUTER(ie) DOT CODE on that model vehical THE MASS AIR SENSOR REGULATES 90% OF HOW THE IGNITION TIMING RUNS I USED TO GET AWAY WITH IT ON OLDER MODELS NOT ANY MORE!?

Aug 30, 2011 | Chevrolet S 10 Cars & Trucks

1 Answer

1998 Jeep grand Cherokee is not getting fire to the fuel pump. What could the problem be?


Open the hood and as you are facing the engine look to the right and you will see a fuse and relay center box. Open the relay center and look on the inside of the cover you removed and it will show you which relay is for the starter and fuel pump relay. Rather than purchase a new relay remove one of the relays from a known good location (all the relays are the same in these locations). Place the known good relay in the suspected bad relays position. If it works your problem is solved. If not and the relay is good then you need to move to the fuel pump in the fuel tank. This can be tricky and if you have not dealt with internal fuel pumps my suggestion is don't start. Remember you are playing with gasoline here and possible personal injury due to fire. Have someone who is competent to replace the fuel pump if necessary. I hope this helped. Also one other thing. If you turn the ignition switch on and you hear a whining noise that will be you fuel pump. This does not mean it is pumping it just means the electric motor to the fuel pump has power to it.

Dec 16, 2010 | 1998 Jeep Cherokee

1 Answer

Car cranks but dose not start, there is no power to distributator or fuel pump


I suspect the at this point, the main relay is defective. This relay controls power to fuel and spark circuits.

The PGM-FI Main Relay is actually comprised of two individual internal relays. When the ignition switch is initially turned ON , the Powertrain Control Module (PCM) supplies ground to the PGM-FI Main Relay. This ground triggers one of the PGM-FI internal relays that sends battery voltage to the fuel pump for two seconds to pressurize the fuel system.
When the engine is running the PCM supplies a continuous ground to the PGM-FI Main Relay. The supplied ground keeps the relay in the "closed" position providing electrical current to the fuel pump, keeping the fuel loop pressurized while the engine runs.
If the engine is not running with the ignition on, the PCM cuts the ground to the PGM-FI Main Relay, causing the relay to "open" and stop the electric current flow to the fuel pump. As mentioned previously, if the engine is not running, the PCM will only supply ground to the PGM-FI Main Relay for two seconds when the ignition switch is initially switched to the ON position.
The PGM-FI Main Relay also supplies electrical power to the Idle Air Control (IAC) Valve and to the fuel injectors.

TESTING


If the engine starts and continues to run, the PGM-FI Main Relay is working and does not need to be replaced.
  1. Locate and remove the relay.

On some models of the Civic and Civic del Sol it is located to the left of the steering column under the dash. Many later models position it either near the passenger right side kick panel under the dash or by the driver left side kick panel up under the dash.
  1. Attach the battery positive terminal to the No. 2 terminal.
  2. And the battery negative terminal to the No. 1 terminal.
  3. Check for continuity between terminal No. 5 and 4.
  4. If there is no continuity, replace the relay and retest

Aug 05, 2010 | Honda Civic Cars & Trucks

1 Answer

I have a 2004 Chevy Impala it has poer at the fuel pump fuse and fuse looks good but no power at fuel pump. is there a fuel pump relay switch or what could it be?


First make a set of jumper wires and jump the pump from the battery and see if it works. If it runs its the relay or the ECU,or the ignition switch.
Remove the relay and test it for B+. Then jump the terminals and see if the pump runs. If pump runs and you got B+ up to this point its the relay.
However,if no B+ at the relay means ECU not giving relay the turn on signal..
While wearing a ground wrist strap check out ECU Grounds and B+ wires for continuity from Ignition switch and other areas of interest (use shop manual)
either the switch is not telling ecu to send message to relay to turn on the pump or someone in this circuit has gone bad.

Mar 24, 2010 | 2004 Chevrolet Impala

1 Answer

2000 Jeep Grand cherokee Laredo wont start. Engine turn over . No noise from fuel pump with ignition on. Replaced fuel pump and filter.Turn ignition on- pump did not run.Jumped the fuel pump at the pump...


sounds alot the the pcm it controls the fuel pump and ign system but the anti theft would keep it from starting because the key has a transponder in it programmed for that vehicle and that would kill all ign if triggered

Sep 22, 2009 | 2000 Jeep Grand Cherokee

2 Answers

Buzzing fuel pump


sounds like the fuel pump relay is stuck on. find the relay and replace it. hope this helps mike

Jun 16, 2009 | Acura TL Cars & Trucks

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