Savage19NRA

2nd owner, 225k miles, E4OD, single tank

​​​​​​Hot start issues similar to vapor lock. After driving and coming up to temp it is difficult to start after shutdown for approx. 15 min, after 30 min. starts OK.
So today I hooked a fuel pressure gage to the Schrader fitting after sitting overnight. Ambient temp. 80 deg. Prestart pressure with koeo; 1 turn of key 10psi, 4 turns 20 psi, pump runs for approx. 1 sec per turn.

Cold engine running, 45 psi, FPR disconnected 45 psi, rev and drops to 42 psi. Vacuum at 20 hg idle

Hot engine prestart koeo, pressure released, 1 turn 8 psi, 2 turns 18 psi, 4 turns 32 psi.

Hot engine running, 45 psi, FPR disconnected 45 psi, rev and drops to 40 psi.

Hot engine off, 54 psi, 1 min 54 psi, holds 54 psi until 15 min then drops to 48 psi after 20 min

FPR replaced 25k back approx 6 yrs ago along with fuel filter. So I'm thinking injectors are OK, FPR OK, filter needs replacing, maybe tank filter\sock next, then high pressure pump.

Does this truck have 2 fuel pumps, 1 in tank and one outside?

What else could I be missing?

justintendo

did you get this resolved?

Savage19NRA

Not yet, but I've had to replace radiator and hoses, so this was put on back burner for the time being.

Chris_1

iTrader: (1)

Your fuel pressure is way low for a 92 6 cylinder. It wants 45 to 60 psi - preferably 55 to 60 KOEO. I would guess your pump is weak.

KurtD

I have a 92 4.9L I6 with 180,000 miles. single tank. KOEO: 1 turn =0 psi, 2 turn = 10 psi, 3 turn = 20 psi, 4 turn = 30 psi, 5 turn=40 psi, 6 turn =48 psi. It will hold 48 psi for a little while and then drop to 46 psi after about a minute and continue to drop slowly.
engine idling = 40 psi. FPR vacuum unhooked while running = 50 psi
The truck starts and runs ok until you try to accelerate in 3rd, 4th, or 5th gear. If you give it a lot of gas, it hesitates and bucks until you downshift and accelerate slowly.

Looking at other posts, are these symptoms of a weak pump?

Thanks

Steve83

They're symptoms, but they don't specifically identify the pump. They're more-likely due to worn spark plugs, improper ignition timing, failing coil or wires, or other ignition system faults. I recommend you buy a Haynes manual, read it, and follow the ignition diagnostic procedure.

Since it has also been bucking, you need to check the engine mounts. They're VERY easy to break.

KurtD

Steve83, thanks for the recommendation to check timing. I have not done anything with timing, but I borrowed a timing light and checked the timing and it was at around 2 degrees. I changed it to 13 and that seems to have fixed the problem. I have been chasing this for a while. Just glad I don’t throw a lot of money at the wrong things. Thanks again for your help.

Steve83

It should be 10° BTDC with the SPOUT jumper removed, as described on the VECI label under the hood.


(phone app link)