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)

I'm new to the 940 with the Rex-Regina system but maybe I can help a little. Is your 940 the Regina model? You can tell by looking at the coil. If it is the familiar cylindar with the spark wire coming out the end, you have a Bosch system. If the coil is a blocky, complex looking thing, you have the Regina-Rex system. The REgina has only one fuel pump and it is mounted inside the gas tank. The filter is under the car on the driver's side. To get at the pump you open a panel in the body to access the tank and I read that it is a PITA.

I've had the FPR soldering go bad on my 240's and I'd sure resolder or replace it if you can see the cracks. Sometimes the cracks are so small you need a magnified to see them. These cracks can cause all sorts of intermittent problems.

I pulled and cleaned the Regina idle control motor yesterday. It is totally different from the Bosch. The Bosch is a small motor which rotates to control the idle air flow valve. The Regina is a solenoid which slide back and forth to control the air valve. I'd think the Regina unit would be more durable.

My 940 has Rex-Regina. The coil has an integrated power stage, and there's no AMM, only the pressure sensor.

The problem is, though, that I was hearing a distinct, separate pump-like noise that was present when the fuel pump(s) got energized. That's why I believe I've got two fuel pumps. Maybe I'm wrong, though, and the in-tank pump was making some weird noises. I will have to pull it out, then.

The fuse label on the ashtray mentions two fuel pumps as well, but that may be irrelevant here (either they use the same label everywhere, or the ashtray was replaced).

Thanks, Kuba

Just a thought - could the "extra" pump sound be the vacuum pump for the cruise control? I haven't had a chance to dig into that yet but there is a vacuum pump located on the left wheel housing tower which is powered by a 12v motor. See if th esond comes and goes with the cruise control on-off switch. If your car has the Bosch main pump, I'd expect to find it under the car next to the fuel filter.

I know on the 940 it is under the car near the driver's seat. I don't know how much that has changed between models, but it might be enough to get you started...

Thanks. I guess I will just pull it out and have a closer look.