[The Lazy Destroyer]

This was from another forum I posted this question on:

I have tried multiple key-on attempts and it doesn't really affect the issue. I believe the pressure drops too quickly between "primes". Also, research is telling me my pump should run for 2 seconds, but from what I can hear it is probably not even one second.

Is there a pump prime terminal on these trucks? On a LT1 car I have there is a pigtail that if grounded will run the pump manually. I suspect if that pump ran longer than it does during prime, it would start easier.

• Short pump priming time
• immediate fuel pressure drop off

I suspect my culprit is here, but not sure where I should start first. Also not sure if the air I saw when bleeding my fuel pressure tester should be an alarm or not.

Could a failing ASD relay cause the pump to prime but not prime long enough than expected?
Or could my problem be the pump itself?
Once running the fuel pump appears to run fine so...

Also the store only had a 0-100psi gauge to rent so my 12psi reading may be off slightly.

 

[The Lazy Destroyer]

Thanks for the reply! Actually after posting that I did some further reading and realized that yes the manual I have is wrong (or at least I read it wrong, which is a possibility), so no vacuum line at regulator. Makes me wonder what else is wrong in that book now...

10-4. I will check injectors first.
If the injectors turn out okay... my possible culprits are pump check valve or regulator.
Regulator is a little pricey at $80. Would an external inline check valve be the next step before looking at the regulator? I like the idea of the external check... cause I hate dropping gas tanks. So if I could resolve the problem without changing pumps that would be a plus.

Any recommendations on what check valve to use, and is this something an AutoZone or Advanced Auto would carry? Quick search only seems to yield vacuum check valves there.

Also, I assume the pump's internal check valve is on the outlet side going TO the TBI? To retain the pressure it builds to supply the TBI? And a failing check would relieve pressure back to the pump backwards through the system? I assume I could add an inline check at the TBI itself (@ supply side)?

Would I be right to try the following in this order:
-Check for any drips/leaks at injector immediately after engine shut-down
-Add inline check valve to fuel line going to the TBI.
-Replace pressure regulator at TBI.

I hated the kit that I rented anyways, so I may just look for an inline adapter w/ the schrader fitting like the rental kit had... that's all I really need for this truck anyways. I have a schrader fuel pressure test kit already. If I had that inline "T" and a smaller scale gauge that would be slick.

 

[The Lazy Destroyer]

Put in the schrader valve kit and then installed the SUR&R check valve that you had linked to.
Tied the check valve in where the fuel filter is, pretty easy location to install.

This seems to have done the trick! Once I turn off the engine the fuel pressure now stays where it was while it was running and does not immediately drop off. So I believe my problem was probably linked to a bad check valve in the fuel pump assembly.

I kept going back to the truck and checking it throughout the day and so far have not had a single problem getting it started now.

EDIT: Might have to add this one to the "cheat sheet" on here

 

[The Lazy Destroyer]

Sounds good, will try this soon. I did not drive it with the gauge hooked up, the most I did was give it some gas while in park. Doing this the pressure dropped slightly but I would expect that I suppose.

If I see a decent drop in pressure, is this usually a sign the pump is weak and/or on it's way out?

I forgot to mention yesterday when checking the pressure this time I also pinched down the return line and the pressure did not build up any higher.

This time I used my personal fuel pressure test kit (not the stores rental unit) since I now have the schrader fitting on there. It was reading 12psi also while running. I still want to find a 0-30psi gauge sometime but I'm more confident now the 12psi is probably accurate.

 

[The Lazy Destroyer]

Thanks for the replies. The fuel filter was replaced when doing my original work a couple weeks ago.

I am not saying the 12psi is "good enough" and I do know that this may still be a problem with the truck.

For now the truck is night and day different as far as starting. I will probably re-try pinching the return line test once I can get a fresh hose on there, the one on the truck now looks pretty brittle so that is on my short to do list, just didn't have time yesterday. I did go through the hoses before starting to make sure there were no leaks (as suggested here earlier) but did not find any exterior of the tank.

But I understand regarding the hose b/w the pump and fittings so I will check that and probably replace it if it comes down to dropping the tank if things get worse. The voltage is a good idea so if I can find the connector near the tank I will see what voltage I can find there.

Will also do a drive test w/ pressure gauge hooked up when I can find more time. I do not normally drive the truck so waiting is no big deal.  I am not sweating much anyways until I can get a 0-30psi on there.

 

[The Lazy Destroyer]

Question: Is there a fuel pump prime connector in the engine bay at all? That if grounded or supplied w/ 12v will run the pump?
I have seen this on a few other models of cars and was just curious. Would be nice to check pressure without having to actually start the truck up if possible.