Sorry for yet another post on this topic

[jeffroid]

Sorry to those of you who could give a flying you know what about my fuel pump. For those of you who might be able to help and care to, please read on.

 

I have just about eliminated fuel delivery issues. Here is what happened:

 

Please recall that my car acted up with the fuel pump "hotwired", bypassing the FPCU for the first time last night. Well, I went to change the fuel pump and found that the ground wire connection at the fuel pump had come undone. I fixed that and started troubleshooting with my volt meter as follows.

 

I took the wire that I had been using as a hotwire and unhooked it from the spot I had been using as a voltage source under the dash. That wire was still spliced into the positive wire from the FPCU right at the fuel pump. I used that wire to monitor voltage at the pump through the FPCU.

 

The FPCU I had been using delivered 8 volts with the key on, and 0 volts with the engine running. I swapped in the spare FPCU from my parts car, and then had 0 volts with the key on and 14 Volts with the engine running. I left the spare one in and took off for a test drive.

 

I hit the interstate and ran it hard. It ran QUITE WELL at first, but after about five miles it started cutting out again. NO change on the voltmeter - 14 Volts to the pump. I took the next exit and pulled into a parking lot without killing it. At idle, still 14 Volts. I got under the car and the fuel pump was pumping. Looked under the hood and the filter was full of fuel. The choke was also open. The car was still in the "run crappy" mode, but never died. I turned the key off, restarted the car, and it was still in run crappy mode. I turned the key off again, waited about five minutes, restarted again and it was out of the run crappy mode. I drove home normally on the side roads without it going back into the run crappy mode again.

 

So, to summarize, I think I have eliminated fuel delivery issues. The car will cut out and begin to run crappy only after several minutes of highway driving, or after driving through town like a moron, flooring it and driving from stop to stop as quickly as possible without getting arrested.

 

Turning the key off and restarting seems to reset it and put it back out of run crappy mode, but not as readily as before.

 

Any ideas ? ? ? I'm almost thinking carb now, but why would turning the key on and off seem to reset it and cure the problem until the next period of high fuel demand?

 

Again, sorry for the long post and HAPPY THANKSGIVING ! ! ! !

[Skip]

Jeff,

I had a similar problem with

my 85 Brat.

 

It would do just about what you describe.

I did what you did with the same results.

 

The problem tuned out to be rust in the petrol tank.

 

It would get sucked onto the pickup sock

and limit the fuel flow to the pump/carb.

 

Let it idle or shutting the car off would let the

pumped volume return to a level where

it was drive able.

 

I put a tee on the fuel line to the carb

and put a temporary fuel pressure gauge in the cockpit.

 

The carb icing may also be a question

No mention of temp when this happens?

Is the warm air tube and it's control system operative?

 

Other problems that will cause this

 

bad ignitor in the distributor

bad coil.

 

Both can return to normal after the

engine cools.

[jeffroid]

Thanks for the help, Skip. Today is a huge step backwards. Now it's just running like dog crap all the time, no "reset" by shutting down and restarting.

 

I don't think it's fuel related now. The filter in the engine compartment stays full all the time. It still idles, and I can see a strong spray of fuel in the throat when I manually goose the throttle.

 

I'm back to square zero and frustrated. I have to take a step back and regroup. I think it might be electrical now.

 

Thanks to everyone that tried to help - I'll be back.

[idosubaru]

how about bad gas or water getting into your tank? i doubt it, but something to eliminate at least.

 

how old is your ignition coil?

 

the engine code connectors aren't connected are they? like the "diagnosis connector" or the "read from memory" connector? sorry i'm not familiar with your model soob, but some have these connectors at the ECU. normally one is green and the other black by the ECU.

 

are you SURE your ignition system is good. electrical stuff is funny, plugs, wires, rotor, cap, ignition coil. when it's running crappy, try this. carry an extra spark plug with you, or go out right now if you're confident it will run bad. pull one spark plug wire at a time and attach it to your *extra* spark plug (holding it with insulated channel locks or gloves) and ground it to something like the motor (away from the fuel lines/filter) and see if you have good spark at each and every cylinder. i did this to a friends honda and the spark was there, but VERY weak and very small. his car barely ran, wouldn't get up to speed....turned out the ignition wires were installed wrong. anyway, that's not your problem but the ignition system has GOT to be good.

 

just to make this longer....here's another story i was trouble shooting starting, idling and running problems with an XT6 last summer. very random in nature, getting warmed up made it worse. i replaced all sorts of stuff, fuel pump, filter, PCV, cleaned my connections, water temp sensor, fuel injector cleaner...no engine codes...probably some other things i've since forgotten. i finally replaced the plugs eventhough they were only a year old. thing ran perfect after that. ignition issues cause more problems than anything else in all the cars i work on....maybe with the exception of battery terminal problems, dirty, corroded and loose.

[jeffroid]

THANKS EVERYONE FOR ALL THE HELP ! ! !

 

I was grasping for straws so I decided to swap the coil from my parts wagon. While doing so, I found the little black wire that runs from the positive coil terminal through the little capacitor to ground was broken.

 

I replaced that and instant improvement. Put it all back together and took it on the highway - runs awesome.

 

I think I still have some issues with the FPCU, but for now it runs great with the fuel pump hotwired. I can dink around with that tomorrow.

 

NOW I AM GOING TO HAVE A BEER ! ! ! ! ! !

 

Thanks again everybody who helped.

[idosubaru]

awesome. i dont drink, you can have a beer for me too. i'd check with some others and see if that bad ground/bad running could degrade the coil at all. i don't know how they work so i have no idea. but be nice to know if that could ruin the coil prematurely. i still have the original coil on my 205,000 mile XT6...i really should replace that sometime soon.

 

i'd pull the spark plugs. clean them and check the gap. with the coil having output problems that may have fouled the plugs up a little.