88 subaru gl wagon. 1.8 spfi, dual range manual tranny. 235k on car, 120k on engine. Starts and runs fair enough but drops power after 15 minutes or so and eventually stammers and stalls while driving. You can start it back up after it dies only to have it repeat the cycle a minute or so later. Ecu throws no codes. No matter how warm it is you have to ease into the gas or it chuggs out and stammers eventually dying if you dont let out. Car ran ok before sitting about 5 years. No vacuum leaks that are obvious though i guess there could small ones around gaskets that i am unaware of. Pretty sure something somewhere is expanding with heat and causing an issue. Catalitic converter or ignition module maybe? At a loss here!  Thx in advance. 

 

I would start by checking fuel pressure after the power loss and stalling begins.

Excellent idea and one base i haven't covered yet because i need to get my hands on a gauge. Now that I think of it i had to smack the pump to get it going after it sat for a long time. I suppose it could be seizing as it warms as well but working fine cold. I do know the filter is ok. Thanks! Just conversing helps me brainstorm.... 

I was going to say new fuel pump required, same line as naru2 is on with the fuel pressure. 

Cheers 

Bennie

The more I think about it the more sense it makes too. Obvious even. It's at the top of my dookie list now. I may feel dumb now but Ill get over that pretty quick if its the culprit. All it would take is one temporary seize as the relay sends its pulse to cause a cutout. Duh! Thanks guys! I appreciate it!

Before you replace the fuel pump, check the CTS.  Coolant Temperature Sensor.   It can fail in a state where it tells the ECU the engine is cold, and the ECU will send too much fuel to run when hot.   No code, unless the sensor goes way out of valid reading range.

Also, fuel pump is NLA, so you are looking at custom fitting a generic FI pump.

Cts checks out ok. Did a few different tests on it and the system. In the end a simple resistor test i found online told me my answer. One of my first thoughts as well. Would've been nice if it had been the issue though lol tho  I checked the MAF as well, seems ok and fairly new actually and replaced the TPS with a spare I had. No change. Dealt with the egr system which was the only thing throwing a code. Also, i found several places online that say they have the  pump including autozone. Ya never know what they really have til ya go to order it tho lol.

Edited October 24, 20196 yr by KE7CWO

I used a Carter pump on one of mine.  Part number on another thread around here somewhere...  Really nicely made pump.

 

I finally got ahold of a pressure tester. 25 psi between the filter and the input hose. Not sure what it should be but it doesnt drop much at full throttle or when the engine chokes and gags, the flow is solid at 24 - 25.

Edited October 28, 20196 yr by KE7CWO

Between filter and throttle body input?  That sounds good, on the high side even.    Iirc, it's supposed to be 21, and even a little low can start to mess with it.   I would not replace the pump,  as it is supplying enough.  The regulator might be malfunctioning.

There is no fuel in the vacuum side of the regulator and not running rich. I read somewhere that means its ok. If u know more ways of testing it tho  im game. I am a bit irritated at this point. Wish I had the cash to do a weber conversion on it so i can huck this obd1 junk out the window lol

The one I had fail was not leaking fuel past the diaphragm.
I cheated, and swapped in a spare to "test" it.  It ran better with the swapped one.  My next step, is I have an adjustable regulator I plan on using.  Have to figure the best way to disable the built in one.  Then I could do tests and experiment to find the best pressure to run at.

When I had the regulator problem on mine, it was starving for fuel.  It just started stumbling badly, then quit while I was driving.  I got off the highway, and started limping along back roads.  Then it quit.  I was about to call a tow truck, decided to crank one more time, and it fired.  Limped it another mile or 2 to work, checked a few more things, and decided to head home early.  It would go with light throttle, die if you tried to get on it at all.

I have had my occasional battles with the OBD1 systems in these, but also, very long runs of no trouble at all.  These are getting hard to run as daily drivers, because many parts are NLA.  Part of why I have 2 that I keep in running condition, so I am not stuck while rebuilding an old part, or searching for a usable used one, or making one.

Since you have decent fuel pressure, I suppose the injector might be having as problem.

Don't remember - did you take a good look at the intake boot for a crack?  If there were one after the MAF, it would be starved for fuel also.

 

One day, just one day, I am going to start measuring the working resistances of various sensors to help establish a ball park figure. Then possibly could feed the ecu what it would like to see if problems improve or change

I had started to plan out a plug in test panel, with meters, etc to do that kind of thing.  Even gathered some of the needed parts.  At the same time, ended up collecting enough spare parts  that doing swap outs was easier.

Thanks again Dave. I will check all that out. You are full of good ideas! No i did not check the boot.

Dave, is there any way you could just gut the inside of your stock regulator so its just a shell, seal it up real good and add your custom one to the outside? probably not huh. Something tells me you thought of that already. A bit of a redneck idea I admit but I have a good excuse, I'm from N.idaho!

Edited October 29, 20196 yr by KE7CWO

Oh, something like that might be possible,  I just haven't gotten to it yet.  I could also make a part on my bridgeport.   I have a few outdoor related things I'm trying to get wrapped up before it gets too cold, then I have to get back to that regulator.

19 hours ago, KE7CWO said:

I finally got ahold of a pressure tester. 25 psi between the filter and the input hose. Not sure what it should be but it doesnt drop much at full throttle or when the engine chokes and gags, the flow is solid at 24 - 25.

Spec is 20-24 psi at idle,so if you have that all the time,the pump and regulator are OK. Must be something else.

To the point I just wanna do a weber swap and i have a way to get a kit. Good idea or not?

So what was it? cause mine is exactly like that issue

Its best to start a.new thread for your problem.   Things that can cause bad running- first things to check, in no particular order -

Bad fuel, Bad coolant temp sensor.  Low fuel pressure, blocked cat.