Question about Chevrolet C3500

1 Answer

Having a problem burning up fuel pump relays on a 7.4 lit. motor. Do you think it may be the oil pressure sending unit that is tide into the fuel pump relay

Posted by on

  • Anonymous Dec 29, 2008






1 Answer

  • Level 2:

    An expert who has achieved level 2 by getting 100 points


    An expert that gotĀ 5 achievements.


    An expert whose answer gotĀ voted for 20 times.


    An expert who has answered 20 questions.

  • Expert
  • 124 Answers

No I think you will find that the fuel pump is drawing too much current.
Also chech that you have the correct relay fitted, should be about 30Amp.

Posted on Aug 02, 2008


1 Suggested Answer

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

A 6ya expert can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
The service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
Good luck!

Posted on Jan 02, 2017


Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

2 Answers

Bravada starts fine but for short trips will not restart after turning engine off. Just cranks but wont turn over. Takes 3 or 4 tries then starts. Any answers?

I would suspect the problem is the fuel pump. It is located inside the fuel tank. Next time this happens have a spray can of starting fluid with you, spray it into the air intake of the engine and see if it starts right up, if it does you likely need to replace the fuel pump.

Jun 14, 2016 | Cars & Trucks

2 Answers

Why my van wont crank with oil light on

This can be a safety feature the manufacturer has implemented in this vehicle. Make sure the oil level is full. Is the vehicle ,making any tapping noises from the top end? ( valve train noise) If oil level is ok, you may have a defective oil pressure switch causing your symptoms. If the engine is abnormaly noisey it is possible there is no oil pressure and further diagnostics will be requred

May 23, 2015 | 1999 Chrysler Town & Country

1 Answer

Where is the fuel pump relay on a 1997 88 oldsmobile

Its in the glove box behind a panal .But the way this system works is its a split curcit and the oil pressure sendind unit is feed from the same fuse and also goes to the fuel pump with B+. Its a safty thing. So if the relay fails while driveing the fuel pump will still get power through the oil pressure sending unit.. The best way to tell if the relay is bad is how long it takes to start cold .If it fires up quick then the relay is good and the problem is likely with the oil pressure sending unit or something else fuel related like the fuel filter or fuel pump . I fit takes a long crank time when cold then it may be the relay because it will take some time to build up enought oil pressure to trip the oil pressure switch and send voltage to the fuel pump. Also all of the relays in the glove box are interchangable all the same so you can test this way to take the fog light one

Apr 10, 2012 | 1997 Oldsmobile 88

1 Answer

Low engine oil pressure on a 1997 cadillac catera. I suspect the sending unit. Would like to check with a manual gauge. Where to tap in to engine oil pressure?

in order to check the oil pressure, you have to remove the oil sending unit, then screw in the adapter of the oil pressure gage, and then remove the start relay or fuel pump relay from the fuse and relay box, under the hood on the drivers side, and then crank the engine over 3-4 turns, and then record the oil pressure, and then disconnect the oil pressure gage, and then re install the oil sending unit, replace the start relay or fuel pump relay, and then start up the car, and check the oil sending unit , to make sure it is not leaking, if your oil pressure checks out within the specs, then you are fine, if it gives you a low reading, then you could have a bad oil sending unit , or a oil pump going bad on you. i would replace the sending unit first, then see what the gage shows.

Jun 13, 2011 | Cadillac Catera Cars & Trucks

1 Answer

REplaced fuel pump still won,t start when its cold it starts right up when its hot the only way it starts when cold is relieve pressure from line 1997 chevey pu . 305 .

Check your fuel pump relay Alot of chevy systems back up the fuel pump power supply through the oil pressure sending unit . So even if the relay is NG the vehicle will still start and run because the oil pressure sending unit is feeding the pump . It also could be a combination of bolth a bad relay and the O P sending unit it needs to build up enough engine pressure to trip the switch inside the sender to send voltage to the fuel pump and it would do this much better if it was cold the oil is thicker

Feb 10, 2011 | Chevrolet 1500 Cars & Trucks

1 Answer

Fuel pump is not working and I would like to know if it is the relay or the pump. Is there a test wire to test the fuel pump by the brake master cylinder. I have three relays in the glove box which one is...

The way this system works is a little unusel. The relay in the glove box is the one on the far left hand side. The relay is feed off fuse # 9 ECM 20 amp 1 ORANGE circuit 440 however it splits before the relay and goses to the oil pressure sending unit witch acts as a back up for the fuel pump power supply still as ORN 440. The connector red 2 490 is the one near the master cylinder and is called the fuel pump prime connector and with the ignition off will test the connection between that point and the motor in the fuel pump however with the key in start or run pisition the switch in the relay will be open because the ground circuit for the relay 1 blk/wht circuit 151 will trip the switch in the relay and the pump motor will be feed by ORN 440 and this will power the pump motor in normal start mode. Now for instance if the pump relay is bad the vehicle will still start through the split circuit ORN 440 that is going through the oil pressure sending unit it will just take longer because the engine needs to build up enough oil pressure to trip the switch witch is a pressure switch inside the oil pressure unit .So the best test for you at this piont is to put 12 volts on the fuel prime connector off the battery and see if the pump runs with key off . If it dose the pump is ok. If not then remove the relay there are 5 terminals on the bottom of it test for a connection between redwire 87A and 30-C1 gray wire 2 if no connection then relay is NG.If this test is good then test gray 30-1C aganst gray 2 120 located at the connector on the oil pressure sending unit terminal D on the connector if you have connection then the fuel pump is NG or has a ground problem between gray 2 ckt 120 and the fuel pump motor ground G410 T 22 at the frame Hopefuly its not the pump but it varywell may be its likely sorry to be so complex i can send you schamitcal information if you want but its a rather complex problem

Jan 29, 2011 | 1996 GMC Jimmy

1 Answer

I have a 1998 S-10 with a 4 banger. The problem is at times it just will not crank. It turns over fine but sometimes it just won't crank up. When it does this after several atempts sudenly it fires right...

The problem is your oil pressure sending unit this sound hard to belive but its true and its the problem. The fuel system works on a split circuit from fuse # 9 power goe's to the relay but also goe's to the oil sending unit as well and the sending unit is the place where the fuel pump is feed from the relay comes into the oil pressure sending unit. A nd the oil pressure unit needs to build up enough pressure from the oil pressure for the switch in side of it ot trip your is hanging up. So the power supply to the fuel pump is being interuped because it is comeing from the oil sending unit.

Jan 15, 2011 | 1998 Chevrolet S-10 Pickup

2 Answers


If it does not have proper voltage,what is the voltage exactly?Also hook every thing to the vehicle,like it is supposed to be,and turn key to the on position and listen,or feel for the fuel pump relay to click on,and click off.Now look for the fuel service port on the fuel rail and remove cap.Depress the valve core to see if there is fuel in the line,it should spray out pretty good,so be careful of fire,and getting it in your eyes.You may have to cut key off and on with a 5 second pause between off and on,off and on.does it have fuel in rail?And does it have good pressure?It should have a good intense spray.If it does,the fuel pressure is fine most likely,good enough for it to start and run.Now if you are certain it is the fuel pump going off,or not getting enough voltage,then look at the oil sending unit.The oil sending unit will have control over the fuel pump in cases of oil pump failure.Check to see if the oil sending unit may be leaking.Sometimes they won`t leak if they go bad,but if it is leaking it needs to be replaced anyway,You will have to unplug it to actually see if it is leaking.Some vehicles have another switch just like the oil sending unit(most of the time it is the same part number as the oil sending unit)that are just for the sake of not letting the car start,much less,run,to save the engine from burning up and ruining the engine.Am I making any sense?Have you noticed any change in oil pressure?You might not see if you don`t have a gauge.But if this helps you figure the problem out,it will be a positive.If the fuel pressure is fine,then look for the crankshaft sensor to be bad,If I can help,let me know,,,let me know how you come

Aug 19, 2009 | 2003 Ford Expedition

2 Answers

! have a(correction): 1995 Grand am. It's not getting power to the fuel pump... The coil, relay, & ignition module are fine. I've just put my 3rd fuel pump & fuel filters on thinking that may

check your oil sending unit if bad then no power to the pump. this is a savor for your car if you loose oil pressure then the pump shuts off .They only did this a few years!

May 31, 2009 | 1992 Pontiac Grand Am

1 Answer


The first thing you should do is to locate the oil pressure switch/sending unit.

This switch serves two functions.

1) provide oil pressure reading

2) disable the fuel pump relay in event of oil pressure loss.


When this switch is failing to provide the correct pressure to the ECU. The wiring harness can overheat and eventually create a short.

ECM2 fuse blow is because the harness is grounding/shorting.


DO NOT drive the truck until you change the oil pressure switch.

After you change the switch,you should spend sometime to inspect the wiring between the fuel pump relay,ECU and fuel pump.

Please post up day on the comment window/page.

I will follow up on it later.

Good luck.

Mar 04, 2009 | 2000 Oldsmobile Bravada

Not finding what you are looking for?
Cars & Trucks Logo

Related Topics:

93 people viewed this question

Ask a Question

Usually answered in minutes!

Top Chevrolet Experts


Level 3 Expert

79024 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22326 Answers

Ronny Bennett Sr.
Ronny Bennett Sr.

Level 3 Expert

6927 Answers

Are you a Chevrolet Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides