Question about 1991 Volvo 940

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1991 940t intermittent start problem. No injector pulse. Disconnect any one injector and pulse comes back - engine starts. Same problem with 3 ECUs (2 563s and a 951 (which has no cold start circuit) Mechanic says 12 volts is measured at the "ground" side of the injectors (pin 18? at the ecu)

Posted by clsnyder on

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5 Related Answers

freetek

Steve Allison

  • 5569 Answers

SOURCE: no pulse at injectors

The normal way that injectors are controlled is via the permanent application (ignition on obviously) to one side of the coil that operates the enclosed piston, and the precisely timed application of ground (negative) to the other side of the coil. The transistors that control this switching under the command of the engine computer are typically contained within the computer itself. Measuring the voltage at the injectors is not productive since the common multimeter is incapable of detecting the very short pulses that activate the coil. Some kind of visual means would be needed to observe this pulse such as an oscilloscope or an engine analyzer equipped with a 'scope.
It's unlikely that all of the switching transistors (or the injectors) have failed simultaneously so either the computer has a problem or there is no fuel being delivered to the fuel rail that feeds the injectors. You should find a pressure regulator that sits between the fuel line coming from the tank that controls the fuel pressure for the injectors. This device seem to be a sore point in many vehicles and can make it appear that the injectors are not working. Many fuel rails have a fitting similar to a tire valve to allow the testing of the pressure being delivered. I would recommend you check this before assuming that the injectors are at fault.  

Posted on Nov 14, 2008

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Anonymous

  • 1 Answer

SOURCE: jaguar x300 no pulse at injectors replaced ecu, what else could i

does it have a spark at the spark plug leads? if no it sounds like the crank shaft sensor!!

Posted on Apr 05, 2009

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Bill Hackett

  • 383 Answers

SOURCE: Little to no injector pulse only when starter is engaged

95-97 Maximas had a problem where condensation from the A/C would accumulate in the a/c evaporator case from the drain becoming restricted or blocked, When this would occur, condensation would drip onto the ECM and a problem would develop with misfire and/or starting. I would look at the ECM where the harness connects to it for corrosion problems. If you find it, there is a chemical spray which can be used to clean the terminals and/or you can clean them, although it is time consuming and difficult to due because of how small the terminals are. After things are cleaned up, lightly coat the connections with a dielectric grease. This will prevent electrolysis.I believe you can buy these at Radio shack and possibly at an automotive parts supplier.
Also a drop in voltage during the cranking phase will cause a weak spark. Your ignition is what pulses the injectors. It takes a minimum of 9.6 volts, but ideally you want at least 10.5 or more during the cranking phase if you want to get a spark worth anything. Check the voltage on the primary side of the coil while cranking the engine.
I'll watch to see if things work out for you, let me know. ....mybunkey

Posted on Apr 18, 2009

Molson02536

Harvey N Tawatao

  • 3854 Answers

SOURCE: 1985 corvette no pulse to injectors

Very important that if you are not savvy of working on your Vette ...you would be better off - taking your car to a dealership for repairs on your trouble codes. However if you feel that you want to, First locate your car's alcl this component is located just below the instrument panel and to the left of the center console. Remove the plastic cover the first two slots to your right are the A & B slots.
The A slot is the diagnostic slot and the B slot is the ground slot. Insert the computer key into these slots if you do not have a computer key, a paper clip or wire jumper clip will do, (with the engine off) this is very important...now only put the ignition key to on ( not start !!!) the check engine light will display a code 12 which is one flash followed by two flashes. This code will be flashed three times ..followed by the trouble code stored in your car's computer.

What ever the code is it will be flashed three times. Have a paper and pencil ready and write down the code.

Code #12: Normal No Codes. 
Code #13: Open Oxygen Sensor Circuit. 
Code #14: Coolant Sensor Circuit Low.
Code #15: Coolant Sensor Circuit High. 
Code #21: Throttle Position Sensor High. 
Code #22: Throttle Position Sensor Low. 
Code #23: Manifold Air Temperature Circuit High.
Code #24: Vehicle Speed Sensor. 
Code #25: Manifold Air Temperature Circuit Low. 
Code #32: EGR System Failure. 
Code #33: Mass Air Flow Sensor High.
Code #34: Mass Air Flow Sensor Low. 
Code #36: Mas Air Flow Sensor Burn-Off Function Fault. 
Code #41: Cylinder Select Error. 
Code #42: Electronic Spark Timing.
Code #43: Electronic Spark Control. 
Code #44: Lean Exhaust indication. 
Code #45: Rich Exhaust Indication. 
Code #46: Vehicle Anti Theft Fault. 
Code #51: Faulty Mem-Cal. 
Code #52: Fuel Calpak Missing.
Code #52(1990-91 Corvette Only): Engine Oil Temperature Sensor Low. 
Code #53: System Over Voltage. 
Code #54: Fuel Pump Circuit Low Voltage. 
Code #55: Defective ECM. 
Code #62: Engine Oil Temperature Sensor Circuit High.

Please remember that if you have the computer key installed in the alcl and you start the engine (you will ruin the engine's computer) only put the ignition to on (not to start).

If you should get a check engine soon display.. you can use the above procedure and codes to buy the right part or at the very least to keep from getting taken for a ride and be made to pay hight prices for some inexpensive module that you could have installed yourself.

If your engine displays a trouble code ... your engine will go into limp mode ..it will still run but very poorly. You might be able to reset the computer if it will not start (just to get home) by disconnecting both battery cables and re-installing them ...this is not recommended ..but if you are stranded it might help unitl you get your car home or to a repair shop..good luck.

Good luck and hope this helps. 

Posted on May 08, 2009

Anonymous

  • 740 Answers

SOURCE: 1993 honda accord 2.2,no injector pulse

This sounds like a main relay problem here is a diagram its located under the dash under steering column its the brownish -orange box in the picture. http://www.tegger.com/hondafaq/mainrelaylocation/7-main_relay_closeup.jpg Good luck and thanks for using FIX YA

Posted on May 15, 2009

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2 Answers

I have no pulse reading on the injectors first the garage said no 5 injector change then ckp sensor more more ????any idea please


Hi Stephen, Im AL the owner of Big As Auto Repair.

Stephen, here's how you diagnose if its the "Engine Controller" OR the "Wiring Itself". If you have or can get your hands on a test light, then here's what you do. FIRST: Unhook the number 5 Injector and attach the test light across the terminals of the connector. Then start the engine and see if the test light is pulsing on and off real fast. If you have no pulse at the connector that plugs onto the Injector, then move to the engine controller. NOTE: before checking the controller disconnect the negative battery cable so you don't damage the controller. NEXT: You'll need the connector still plugged in for the test, so remove the connector from the engine controller and back probe from the back of the connector the number Injector Circuit. NOTE: DO NOT probe on the side that plugs into the controller, do it from the back side. NEXT: Plug the connector back into the controller and start the vehicle. If you do not have a pulsing light then the engine controller for the number circuit is bad and will need a new controller. If you DO have a pulsing light then its in the wiring OR the connector at the Injector. If you have OR can get your hands on a DVOM which is a digital volt meter you can check which wire is at fault. Here's how. Disconnect both connectors at the Injector and the Controller and put the meter on OHM's then you can probe each wire from the Injector to the Controller to see if the wire is broken. If the meter has a beeper you will hear it beep, if it doesn't you will have a reading on the meter. When you find the wire that's broken run a wire from the Injector connector to the Controller Connector by wiring to the wire coming out of the back of each connector. If you should need further assistance please visit my auto-repair-website its free: http://www.bigasautorepair.com/

Dec 01, 2015 | Cars & Trucks

1 Answer

What causes o low injector pulse


Is that static pressure with key on, engine off? Or engine running pressure? Both should be near 60, usually key on, engine off pressure will be about 3 or 4 psi higher.
If it runs good after starting, the injector pulse must be good. No reason why starting and running pulse should be different. Only difference is when running, fuel pump power is kept on by the oil pressure switch, whereas in starting, the fuel pump relay keeps the pump on. Very unusual, let us know. Measure voltage at one of the injector's power wire with key on. It should be battery voltage or very close.

Aug 22, 2015 | Cars & Trucks

1 Answer

Why do I suddenly have no injector pulse?


Is the vehicle equipped with a security system that may be tripped? If so, the injectors will shut down. The injectors are grounded by the PCM . You may have an internal Issue with it. Is the spark also shutting down when the injectors aren't working? If so, this could be a crank shaft sensor failure. Is there any diagnostic engine codes that can be retreived to possibly isolate the problem?

May 10, 2015 | 2003 Chevrolet Silverado 1500

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Acura mdx misfire


could be a fault in the #3 injector wiring, with the engine running back probe the wiring at the injector with a led trouble light it should glow at each pulse. a pulse can be felt by holding the injector if you have no light. compare with # I&2.

Nov 30, 2014 | 2001 Acura MDX

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89 camaro 5.0 tbi injector pulse intermitant


What have you checked? I would start with a noid light to see when the two injectors wiring is pulsing. if intermittent then i would check the pickup coil located inside the distributor. It controls timing for the injectors and for the timing advance.

Oct 18, 2014 | 1989 Chevrolet Camaro

1 Answer

My 1990 Toyota's #3 cilynder makes no difference with spark plug wire disconnected.


Yes you can test the injector pulse signal with a tool called a "NOID LIGHT". You can buy this handy little tool at any auto parts store like NAPA or Carquest for about $5, it plugs into the injector connector and flashes each time the injector is commanded to open by the processor. I personally think you have a defective wiring harness on the engine.

Jul 12, 2012 | 1990 Toyota Pickup

2 Answers

I have a 92 dodge stleath that isn't getting gas. The fuel pump is working. What could be the problem?


well you could have a bad fuel filter, bad fuel pressure reglator, or even bad injectors.

May 07, 2010 | 1992 Dodge Stealth

1 Answer

After timing belt check light is on. code p0303 and p0304 why?


the P0303 code is for cyclinder #3 possible causes: -defective spark plugs, ignition cables, ignition coil. or flywheel/pulse wheel. -blocked/leaking injector -uneven compression -leakage between the cooling system and cyclimder moisture,flashover in the ignition system on HT side intermittent open-circuit, intermittent short circuit to tje ground,intermittent short circuit to the voltage supply, contact resistance or loose connector in the ignition system low-tension side, in the injector circuit or fuel pump circuit -fuel stoppage -water in the sparl plug wells - contaminated fuel or incorrect fuel type -repeated cold starting where the engine coolant temperature (ECT) has not reached nomal operating temperature between start P0304 is for cyclinder #4. Hope this can help you, please put some rating

Apr 13, 2010 | 2002 Volvo S40

1 Answer

Ok i had a p0302 and then i changed plug wires coil packs the icm injectors camshaft sensor and now i can a p0301 code.. and when i clear the code it will come back with the same code or else a p0300.. im...


1. Freeze Powertrain Control Module (PCM) and see if the problem can be duplicated.

2. Wiggle tug test wiring for #2 injector.

3. Scope the #2 injector for a glitch when the misfire happens. 1. Test for the Exhaust Gas Recirculation (EGR)/coolant adapter gasket leaking EGR gases past the gasket.

2. Connect a vacuum pump to the MAP sensor, block the vacuum source, reset fuel trims, start the engine and add typical vacuum to the MAP sensor and check operation.

3. Test the spark output with 2 High Energy Ignition (HEI) testers, at 25 KV air gap each, at the spark plug wires to ground at wires 2 and 3, then 1 and 4 at cranking speed and engine running.

4. Test the fuel injector pulse width at the injectors compared to the scanner data.

5. Disconnect the O2 sensor, reset the fuel trims, test the system operation in open loop, test injector pulse width. Compare to the closed loop operation injector pulse width and engine operation.

6. Test the Powertrain Control Module (PCM) powers and grounds during the problem.

Oct 13, 2009 | 1996 Chevrolet Cavalier

1 Answer

Not starting......


If the above information is correct.
1. Good Compression
2. Good Spark & Proper timing
3. Good fuel Pressure, injector pulse , injector spray, & fuel quality( no t contiminated)
4. Proper & clear air intake into engine
Then the likely cause would be a restricted exhaust. disconnect the exhaust at the manifold, and retry starting engine. keep me posted, we will make her run!

Jan 13, 2009 | 1994 Mazda MX-3

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