4.3L GMC Safari spider injection/FP - anybody have experience?

[Bob Kontak]

Forgive this ramble but if someone can save me from dropping the tank and replacing the fuel pump, it would be appreciated. Specific questions at bottom of thread.

Van (2003) should have 55-65 psi fuel pressure but 50 psi seems to be the cut-off for proper function from internet reads. Something about tappets in the spider injection need strong pressure.

Pump builds to 55 with key turn then rests at 52. Starts like a boss. Residual pressure will drop to 8psi if left overnight. I don't think it's a leaker.

Once started drops to 48 yet runs fine until highway speeds. If "floored" at 70 will drop to lower gear and surge but then peter out. Have to keep it at sixty to get to your destination.

I have no smell of gasoline. Much talk about fuel lines under manifold and FP regulator leaking yet residual holds.....long time. FP regulator increases pressure then drops below the 48 then back to 48 quickly when throttle blipped. That seems ok to me.

Fuel filter replaced.

Questions:

Can a fuel pump function with adequate power and ground yet deliver a nice steady marginal fuel pressure?

Power at FP cannot be tested unless tank is dropped. If I am into it that deep a new FP is going in. However, ground is accessible. Can a poor ground cause the FP to work "just fine" save not enough pressure? I believe it can.

Can a tired FP regulator drop pressure into a marginal range but not leak?

I would rather pull the tank than open that intake manifold in a van through the dog house hole but I am listening.

Thank you for input.

Edit: Left and right bank OBD lean codes.

[LakeCleElum]

Had motorcycle do this when fuel pump going bad. Only on a hot day with less than 1/4 tank of fuel left....Quick fix on a trip was to keep tank full.

Mech told me that this is caused by driving too much with the fuel light on - pump being exposed and overheating. Replaced the pump inside the tank and problem solved....

[908/930]

No experience with that vehicle, just wondering if you could check the amount of current draw at the fuel pump fuse and compare it to another similar truck? I think it would give you an idea of the condition of the pump and connections.

[fastfredracing]

Its been a while, but I worked on a ton of these . From what I remember, they struggle to start correctly when the pressure falls much below 55 psi. I think they will still run fairly well on lower fuel pressure once they start . Maybe down in the 50's
It really sounds like you need a fuel pump.
Have you driven it with the ye ole fuel pressure gauge duct taped to the windshield trick to see what is happening when you loose power ?
Popping the top off that intake is not that bad of a job. You will need new o rings for the fuel lines, and there is an upper gasket set . It is not like taking off the whole intake . You can probably off an on it in a few hours in that van.
I do think I remember that fuel pressure would bleed down when they were leaking. Like you could watch the gauge drop
IF the lines are leaking in there, there will be fuel puddled and it will be easy to spot. . I remember this was fairly common . It may suck a little bit more in a van.
The other place I always used to look for weird drive a bility problems when I would get stumped, would be the cat .
If you cannot figure anything else out, loosen the flanges at the exhaust manifold, and see if you have full power back .

[Jeff Alton]

Is your the return system or returnless system?

[Geoz1]

Originally Posted by fastfredracing

Its been a while, but I worked on a ton of these . From what I remember, they struggle to start correctly when the pressure falls much below 55 psi. I think they will still run fairly well on lower fuel pressure once they start . Maybe down in the 50's
It really sounds like you need a fuel pump.
Have you driven it with the ye ole fuel pressure gauge duct taped to the windshield trick to see what is happening when you loose power ?
Popping the top off that intake is not that bad of a job. You will need new o rings for the fuel lines, and there is an upper gasket set . It is not like taking off the whole intake . You can probably off an on it in a few hours in that van.
I do think I remember that fuel pressure would bleed down when they were leaking. Like you could watch the gauge drop
IF the lines are leaking in there, there will be fuel puddled and it will be easy to spot. . I remember this was fairly common . It may suck a little bit more in a van.
The other place I always used to look for weird drive a bility problems when I would get stumped, would be the cat .
If you cannot figure anything else out, loosen the flanges at the exhaust manifold, and see if you have full power back .

Excellent advice! Add a spider to stock. It will need it.


Put a fuel pump in it.

[DanielDudley]

If there is varnish on the screen, Techron will clear it. Had this problem with an 04 Silverado.

Try the simple solutions first.

[Bob Kontak]

Originally Posted by Jeff Alton

Is your the return system or returnless system?

Return system.

The van is drive-able and will be driven this week. Next weekend is the repair window so I will get Techron or Seafoam in the tank tomorrow.

Amp draw test is good thinking.

Thanks for the write-up Fred. I was hoping you would respond.

[Sooner or later]

Fuel filter?

[Bob Kontak]

Originally Posted by Sooner or later

Fuel filter?

Fuel filter and PCV valve replaced. PCV valve sounded like an angry rattle snake. It alone could have triggered 0171/0174 lean codes.

[Dansvan]

Take it for a drive with the MAF unplugged for grins. See what happens.

[Bob Kontak]

Originally Posted by Dansvan

Take it for a drive with the MAF unplugged for grins. See what happens.

Car does run with MAF and snorkel on bench. It did throw a specific MAF sensor code with it unplugged. Also cleaned it.

Just got tags for it Friday and I drove it illegally for short runs on more rural roads before that. Never hit the higher speeds where it demonstrated symptoms.

I'll try it Saturday along with other suggestions first. Betting fuel pump or fuel pump ground given no fuel smell and favorable residual pressure.

[Bob Kontak]

Fuel pump assembly purchased. Two types from factory so had to leech off the dealer for info based on VIN. They wanted $500 for the high volume one and $400 for the every day one (my version). Still had to pay $230 for the one from the FLAPS post discount. Van finally coming back to shop this Saturday.

Reason I am posting is I tell my kid (it's his employer's vehicle) that best not to put anything but $10 at a time in for gas. He says, I just filled it up this morning. How much gas, my Son? 22 gallons says he.

Great googly moogly.