Fuel pressure issues

[Seattleboy25]

FSB Brothers -

Been reading and learning from FSB for the past two years. Great forum and appreciate all of the great advice and information.

Have come across an issue that I need some advice on. Have done several searches and am not finding this exact problem.

Started about a week ago when making a 400 mile drive. Truck had very little power when going up hills at highway speed. Pulled codes and only found a KOEO Code 34 - ECT sensor fault which I don't feel is creating this problem.

Checked plugs - all fine. Has newer spark plug wires and cap and rotor. Getting plenty of spark. Thought that one of the cats may be clogged - seafoamed the engine and got plenty of smoke from the exhaust. Fuel pressure was 40 psi key on at the rail and 32 psi with the engine running.

Buttoned her back up and began the drive back home. After I went about another 100 miles, engine just started having less and less power to the point that I could barely go 25 mph up a slight (3 percent) hill. Had to keep rpm's between 1100 and 1800 to make any forward progress. Truck began missing slightly. Funny thing is that it idles normally - no difference.

Got home, checked the fuel pump relay, all good. Checked the fuel pressure at the rail again (key on - engine not running) and first test was 40 psi, second test immediately after was 20 psi, third was 10 psi and fourth was 0 psi. Changed the fuel filter and retested - same results. Thought okay - maybe it is the FPR. Checked that and appears to be working just fine (no smell of gas in vacuum line). Next step was checking the high pressure (frame rail) fuel pump output - tons of fuel poured out when key on. Removed the high pressure fuel pump (did check and was getting power at the pump). After removing high pressure fuel pump, cranked the engine over (made sure to reset the inertia switch) and there was absolutely no fuel coming from the tank fuel line.

So here is my question: given that the performance dropped off over a few hundred miles, I assume the in tank pump has gone out and needs to be replaced (oh joy). Can the truck still idle okay even with the in tank pump inoperable? Seems that it would idle rough or not at all.

Also, I can't seem to find the reservoir that is mentioned on the FSB forum.

Do any of you wisemen have any other potential causes? Truck only has 90,000 miles on it (yes, it's been garaged a lot). Appreciate any advice.

Also, checked compression on all cylinders and ranged from 169 to 180.

[Seattle FSB]

Test your Throttle Position Sensor (TPS). Also, clean and test your Exhaust Gas Recirculation (EGR) Valve for proper operation.


See these links:

Throttle Position Sensor Testing, Replacement and Adjustment

hunting for a solution here

[Seattleboy25]

Thanks Seattle FSB. Would either of those affect the fuel pressure as measured at the rail?

[Seattle FSB]

It could affect Air/Fuel Ratio. I am not sure that fuel pressure is your issue. Read the links.

[Seattleboy25]

Read the links Seattle FSB but I'm not getting any fuel pressure from the in tank pump. Easy assumption is that the in tank pump is out. Just wondering if anyone else has other potential causes.

[phobos2deimos]

Not sure, but I'd run codes first. I have the *exact* same symptoms you do and still haven't gotten around to solving it, despite trying. I've got a code 41 (lean) to go with it.
I don't have any fuel pressure issues at a standstill, although I can't see the FP gauge when I'm going uphill. Keep us updated if you solve it!

[Seattleboy25]

Well gents, today is the day I'm replacing the in tank fuel pump. Stay tuned.

[phobos2deimos]

Originally Posted by Seattleboy25

Well gents, today is the day I'm replacing the in tank fuel pump. Stay tuned.

Thanks for keeping us posted. For your sake and mine hope this is the issue!

[96EB5.8]

A little late but yes the tank pump being out can cause that problem. the less fuel in the tank the worse the problem will be.

[Yankeefan]

Hey Seattleboy, any updates? I have been following this thread as I have the same issues.

Was thinking either clogged cats or the in tank sock filter is clogged. Just wondering if you solved your problem.

[phobos2deimos]

Updates?

[Seattleboy25]

Well gents, problem located. The catalytic converter was totally plugged Ran a backpressure test from the O2 sensor port and instead of being 5 psi, it was 20 psi! Cat totally clogged. Also have a cracked exhaust manifold on the passenger side. Off to shop Summit for new headers and exhaust. Any recommendations on shorty headers??

[TheUnforgiven]

The clogged cat does not explain your lack of fuel pressure at the rail.

[Seattleboy25]

Lack of fuel pressure at the rail was corrected with a new high pressure fuel pump.

Originally Posted by TheUnforgiven

The clogged cat does not explain your lack of fuel pressure at the rail.

[phobos2deimos]

Thanks, appreciate it!

[Cantflysolo]

Thanks for posting this. I think this is the same problem I am having right now too and plan to look into it further now.