Low Fuel Pressure

[aball4620]

My '88 2.9 with dual tanks is still giving me issues after replacing the head gasket. It starts fine, and tries to idle but surges constantly. The rpm's won't climb above about 1900-2000 with the throttle wide open, and it constantly stumbles while idling and until it is warmed up will periodically stall. I'd been dealing with some quickly dissipating white smoke out of the tail pipe for the last couple years as well as horrendous gas mileage (about 7-8 mpg). This has/ had the crack prone heads so I replaced the heads with new clearwater heads and all the gaskets. Will limp out of the uphill driveway, but is not drive-able.

The fuel system was totally FUBARed by the previous owner and the most recent discovered was a kink in the feed line between the tank selector and the reservoir, as well as some sort of failure/ clog in the return line valve inside the tank selector, which was causing pretty high back pressure. It currently has a new pump and fuel relay and a new harness and does turn on for the 2 seconds each time the key is turned. But, pressure will not climb above 36 psi no matter how many times I cycle the key. I understand that pump should go to 50-60 no problem. The FPR is new and dry. I hear some sort of gurgle coming from what sounds like the reservoir once it hits 36 psi. This happens on BOTH tanks - meaning both lift pumps. Pressure bleeds to about 32-33 after an hour and down to about 25 after 24 hours. Codes are inconsistent, meaning sometimes they show up and sometimes they don't. Typically they involve the TPS - which is new and the circuit has been checked. Injectors are new and tested for leaks - they look fine. The truck acts like it is starving - possibly both low pressure pumps have failed and the high pressure pump is exhausting the reservoir? I'm at a loss. Anything standing out?

 

[Nelson and Hudson]

Fuel filter?

 

[rusty ol ranger]

36 PSI is in spec. The 2.9 needs 32-40 to run properly.

Id be getting me a timing light...ill bet its out of time like a SOB. Pull the SPOUT connector and see if it makes a difference.

Also, buy an EEC IV code reader and pull codes, you might get lucky.

 

[aball4620]

Fuel filter?

Brand new. Replaced one that was only a year old in hopes of throwing parts at the problem.

36 PSI is in spec. The 2.9 needs 32-40 to run properly.

Id be getting me a timing light...ill bet its out of time like a SOB. Pull the SPOUT connector and see if it makes a difference.

Also, buy an EEC IV code reader and pull codes, you might get lucky.

Timing is dead on. I've checked and adjusted probably half a dozen times because I, like you, thought this had to be a timing problem. Brand new distributor, rotor, cap, wires, and coil just because why not. 10 degrees tdc with spout removed. I've even played with taking it up and down and doesn't seem to like it - this is the "best" it runs. 180 degrees out won't even fire.

It is certainly possible that my gauge is reading a few psi low - perhaps the real numbers are more like 32 and 39. I'll pick up a rental from the local parts store and compare.

I have an OBD1 reader. The only code is 63 in continuous memory with KOEO. Brand new TPS (yes that has been tested because I'm aware that new doesn't mean working) running ~0.8 - 4.55 volts. Anyway, the last TPS gave the same reading. I've found a few others and replaced parts as needed - notably the o2 sensor (which was new a couple years ago but apparently fouled), and the air charge sensor. So lucky there, but only slight improvements in idle.

 

[rusty ol ranger]

You checked compression?

 

[aball4620]

You checked compression?

Compression is good. Don't have the numbers right here but all are around 180 with one oddball at 169 if I remember.

 

[Dirtman]

36 PSI is in spec. The 2.9 needs 32-40 to run properly.

Id be getting me a timing light...ill bet its out of time like a SOB. Pull the SPOUT connector and see if it makes a difference.

Also, buy an EEC IV code reader and pull codes, you might get lucky.

No it needs a new ECM. Everything needs a new ECM!!!!!!

 

[rusty ol ranger]

Vacuum test? Off chance the exhaust is plugged up?

 

[aball4620]

Vacuum test? Off chance the exhaust is plugged up?

No the exhaust had too many outlets PO knocked out the cat. The vacuum seems to hold steady at about 18-19 but with it surging and stumbling the vacuum obviously fluctuates too. Introducing new leaks makes it die. I’ve replaced most of the vacuum hoses just to be sure with no changes.