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Hi folks.
I have a rather funny fuel pump situation. First of all, the fuel pump relay solder joints are cracked so I have to re-solder them first. But for now, my problem is that when I turn the key to II, both fuel pumps will start for 1 second or so, just as they should. The noise they make seems very normal. Now, when I start the engine, the in-tank pump will run fine, but the main pump sputters and dies after about 5-10 seconds of running. Basically my car runs on the in-tank pump, and obviously it's showing decent signs of running lean. Power loss, which I'm experiencing, is partially due to dead knock sensor, but really the main pump doesn't run so the amount of fuel it gets from the in-tank pump makes the engine seem like 50hp. It will go up to 75mph full throttle.
Now, assuming that resoldering the relay fixes the problem, or there was no relay problem at all, I have following questions:
1. Where's the main (out-of-tank) pump? I have read somewhere that Rex/Regina cars have only one pump. I can distinctly hear two fuel pump noise sources, and one of them dies as I explained above. The reason I ask is since there's no noise source, it's hard to see where the main pump is. I know where the tank and the fuel filter are. Didn't bother jacking up the car yet.
2. What does it take to remove the main pump? Any special tools/tricks?
Assuming that the main pump has a standard commutated DC motor, I guess it could be dying due to worn brushes and/or commutator problems, so I hope I can at least make some difference there. Hopefully the pump itself doesn't seize -- will check that once I get the pump out, obviously. When it runs, the noise it makes seems pretty normal to me -- just slightly louder and higher-pitched than the noise of the in-tank pump, but no unusual irregularities. Just a steady little whiny noise. And then it "sputters" for about a quarter of a second and stops.
Removing the in-tank pump fuse makes the engine stop almost instantly, so it's really the in-tank pump that keeps the engine fueled. Poor one, working so hard :). As far as engine temperature goes, it seems to run lean because it warms up much faster than it normally used to (lean mixture gives higher combustion temps, right?).
I don't want to keep it much longer like this, since I don't want to fry the valves, and I want to get my power back too :) It's snail in acceleration.
Thanks for all hints,
Kuba
'93 940, 136k
Symptom status in a nutshell
- knock sensor seems intermittent -- knock sensor failure/absence code appears about once in a week, will diagnose again after getting fuel pump to work
- fuel pump relay solder joints (on the PC board) have mechanical/thermal fatigue cracks, will resolder before touching the main pump
- main pump works fine for 1s pre-pump interval, sputters and dies 5-10s after starting the engine
- occasional adaptive lambda too lean/rich during idle code appears once in a week; somehow together with knock sensor code -- can this indicate lean misfire?
- the engine runs quite rough in idle although it doesn't have any real tendency to die, it always stays above 600 rpm, most of the time in 700-900 rpm range, doesn't go above 900 although it used to (maybe when the pump was intermittent instead of stopped all the time -- I didn't listen for it)
- rough idle but I guess not much can be done before the main pump starts working and the injector pulse duration gets back to reasonable values; probably that's what could be giving adaptive lambda code during idle
Do I make some sense in my reasoning above?
FYI: Maintenance status
- distributor cleaned and checked, looks good enough to me
- new plugs and wires
- spark is bright bluish white
- throttle body cleaned, TPS readjusted
- IAC valve cleaned and checked -- regulates just fine
- fuel filter may be old, but I have to get main pump to run first anyway, and since the in-tank pump delivers enough fuel to keep me running with poor acceleration, it seems that the fuel filter is not plugged solid at least :)
- using 98 Amoco fuel all the time, ran STP Treatment through one tank 3 months ago, oil is 15W40 although I will switch to synthetic soon
- compression is perfect, old spark plugs had no signs of oil in the cylinders -- they were just old and worn (3 of them must have been the original volvo ones that came with the car)
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