fuel pump relay problem

[racint]

I am having a problem burning up fuel pump relays on my 1998 c3500 truck with a 7.4 lit. . I am thinking it may be the fuel pump drawing to many amps. It started out doing it once in awhile. Now on my last trip it burned out one about every 150 miles. Could there be anything else causing this?

[j cAT]

Originally Posted by racint

I am having a problem burning up fuel pump relays on my 1998 c3500 truck with a 7.4 lit. . I am thinking it may be the fuel pump drawing to many amps. It started out doing it once in awhile. Now on my last trip it burned out one about every 150 miles. Could there be anything else causing this?

chafing wire.....inspect the wires for damage.....also remove fuse and place ammeter in the fuse pins to measure current ....I don't know exactly how much it draws perhaps another member has this amperage..

[brcidd]

high pressure pumps (61 psi) draw 8-9 amps , lower pressure pumps are usually 6 amps or so..

Those 454 engines are hot ones- Mine melted the oil pressure sending unit- which is also a fuel pump switch- drew amps through it- ran my battery down a lot- until I found what was going on- perhaps your sending unit is the problem-the fuel pump cicuit runs through it you know- in parallel to the fuel pump relay-- those engines just run so hot- anything plastic can melt-- heck- I even melted the rotor off my distributor!!

[MT-2500]

Welcome to AF.
The fuel pump relay should be fused.
If overloaded it should pop fuse.
Not relay.
Is it burning up relay inside?
Make sure it has a good right amp fuse on circuit.
If a oil pressure switch on fuel pump circuit check wiring to it also.
As said Check amp draw on fuel pump circuit cold and hot.

Are you using good quality relays?
MT

[racint]

The relay does not look burn't up inside Pin 30 and plastic is melted and it is getting very hot. When the truck cuts off going done the road and you go to put a new one in you can't hold on to the relay it is so hot. I will try the things you all suggested and let you know what I find. Thank you

[racint]

I checked all the wires and they were ok except there are 2 going back to the fuel pump I think that somone had put butt connectors on them, they are tight but had nothing over them to keep weather out. I checked the amp draw on the fuse for the fuel pump and it was 10.5amps. That fuse says for fuel pump and ecm. There is no fuse just for the fuel pump. Were is the oil pressure fuel pump switch located. Do you all think it may be that.

[j cAT]

Originally Posted by racint

I checked all the wires and they were ok except there are 2 going back to the fuel pump I think that somone had put butt connectors on them, they are tight but had nothing over them to keep weather out. I checked the amp draw on the fuse for the fuel pump and it was 10.5amps. That fuse says for fuel pump and ecm. There is no fuse just for the fuel pump. Were is the oil pressure fuel pump switch located. Do you all think it may be that.

those butt connectors are no good ....if the crimp is poor and with these connectors it will be especially so outside exposed to the weather..


the current of 10amps is on the high side...

[777stickman]

Pin 30 on the relay is the power feed out to the pump. When the relay is energized power from the ECM B fuse goes thru relay pin 87 to pin 30 and to the pump.

The signal to energize the relay comes from the VCM/PCM

I really don't think the oil press sw is a problem, but ??

1st thing is to replace those splices with weather tight ones (heat shrink ones are available). You may have to splice in some new wire if there is substantial corrosion around the current splices.

Corrosion causes resistance and resistance causes heat in the circuit.

[racint]

Thank you for all the suggestions. I will fix the butt connectors with a weather pack connector. The fuel pump is awful noisey also. and the gas gague is flickering back and forth all the time. Do you think the full pump is weak also being that it is drawing so many amps.

[tibmulp]

I have no power to my new fuel pump. 2002 sliverado

[MT-2500]

Originally Posted by tibmulp

I have no power to my new fuel pump. 2002 sliverado

Welcome to AF.
With your problem you need to start a New Thread if you need help on it.
Saves high jacking another Thread,
MT

[MT-2500]

Originally Posted by racint

Thank you for all the suggestions. I will fix the butt connectors with a weather pack connector. The fuel pump is awful noisey also. and the gas gague is flickering back and forth all the time. Do you think the full pump is weak also being that it is drawing so many amps.

Get good wiring to it. Power and ground.
Throw the butt connectors in trash can and solder wiring together.
Check fuel filter.
A plugged fuel filter can overload a fuel pump.
Run a good fuel pressure check 56/62 specs.
Post back fuel pressure readings.
MT

[racint]

I fixed the wires, and changed the fuel filter also. I took a fuel pressure reading. with the key on and it primes up to 58 psi and drops back to 50 when you turn the key off. With the truck running the pressure is 46psi. Are the pressures to low... I have been busy and don't drive the truck very much this is why it took me so long to get the pressure readings. I havn't burn't up a relay yet but I have not driven it very much either.

[MT-2500]

Racint
Thanks to the link I found your post.

In looking over the post your amp draw is high as stated by J cat.

Extra Noise from fuel pump and low pressure points to bad fuel pump.
But first check fuel filter.
And pressure regulator.
Then run a full fuel pressure test.
Specs are 56/62 on it.
You should have around 58/60 running on the road.

The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
Until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressures.
Cold start should be around 60/62 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 56/62 lbs pressure depending on engine load.
Full pressure with return pinched off should be 85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post-back fuel pressure readings.

Remember a fuel pump pressure regulator controls the pressure and maintains a steady pressure depending on engine load and vacuum.
It has to be capable of producing higher pressure than the regulated pressure.

The fuel pressure regulator controls pressure and can leak off or bypass pressure

Also check that amp draw when cold and when the pump is hot after a 30 minute run and also when pump is up to par on pressure.
More pressure the more amp draw,

If your fuel pump does not pass the test I would replace it with a AC-Delco/Delphi fuel pump module.

Also there has been some wiring problems with wiring melting down inside pump unit and at the plug in.

The new pump may come with a new wiring plug.
If so solder wiring and heat shrink solder joints and stager splices so they are not next to each other.

Post back full pressure readings and amp draw test.
Good Luck

[racint]

I did recently replaced the fuel filter then I took the fuel pressures. They are on the post two up from this one. I recently replaced the regulator with in 2000 miles ago. I was having a hard time starting it and when I put intake gaskets on I found fuel in the regulator vacum line so I replaced it and the vacum line also. It took care of my had to start problem. It looks like it has good fuel pressure at prime just low running. I will look into putting a new fuel pump with sending unit also since my fuel gague is fluttering also. I will only put a fuel pump on from the dealer. Thank you