The nightmares begin.

[rs74]

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Originally Posted by ChevyTech

54 Jimmy is correct that missing or poor grounds can cause all kinds of running problems.

There should be a ground between the back of the passenger side cylinder head and the fire wall. There should be a ground strap and a ground wire that goes into the harness.

The ECM and engine sensors ground at the front of the intake manifold under the front intake bolts/studs or by the thermostat.

A 1993 should have a ground between the negative battery cable and the fender.

I have the battery to fender ground on. The strap for firewall to rear head I have. Still looking for a ground strap for frame to front of head. I think this strap is supposed to be heavy gauge. Now what about the one you said has a ground strap and wire going into harness. I am not seeing this.

[rs74]

This is the only ground that I see coming from the harness. It grounds next to this relay.

[rs74]

Anymore feedback on this? The stud that is under the heater hoses is from what I could tell where the ground strap ran from to the rear of the head. That stud is broken off. Is it okay just to ground anywhere on the firewall or was that stud for something important? Everything else is hooked up ground wise unless there is supposed to be a strap and ground wire from the harness. Truck is still running like garbage.

[rs74]

I robbed another distributor and EGR valve from another engine and threw on mine and still no difference. Finally tracked down a TBI fitting for a fuel pressure tester. Called three different parts stores and nothing in stock. Going to try to check fuel pressure. I even swapped out the map sensor too and nothing. I think I am down to fuel pump, fuel pressure regulator, injectors or computer.

[ChevyTech]

I have been busy with no time to get to the boards.

You are ruling things out so you are making progress.

Check the fuel pressure, and it that is good, testing the engine compression would be a good idea

I will try to get back to the board soon. Sometime this weekend I should get here at least once.

The ground from the harness by the back of the passenger side head comes out of the harness within a few inches of the spot where the ground strap goes.

[iluvmy72]

I have no clue why GM insists on painting over the ground.

[rs74]

Might be on to something here given this fuel pressure tester gauge is good. It only has about 6-8 psi when at idle and it drops to about 4 when pushing on the pedal. So looks like I am ordering a fuel pump.

As far as that ground I will look again but I didn't see anything back there the last time I looked. I will open up the harness and look a little more thorough this time to make sure.

[speedygonzales]

The first thing you should do BEFORE replacing the pump is restrict the return line. If the pressure comes up to what it should be, chances are the problem is the fuel pressure regulator.

The diaphragm and spring corrode and get stiff and easily don't regulate the pressure. However, I strongly suggest you confirm the gauge reading before doing any of that.

[ChevyTech]

I agree with speedy that you better do the diagnostic testing before you just go ahead and replace the fuel pump.

There are failures other then the pump that can cause low fuel pressure.

Here is a thead with testing instructions:
http://67-72chevytrucks.com/vboard/s...d.php?t=375132