Need help with fueling issue…..electrical suspected

im4duke · 11-13-2011, 04:55 PM

Coming home one afternoon, my idle dropped while cruising at 30 mph and the car stumbled as I gave it gas. It lasted about 5 seconds, then back to normal. It has been intermittent since. Mostly noticeable at lower RPMs, especially when starting from a stop. Sometimes it happens when the car is cold, sometimes when hot after 20 minutes of driving. A couple of times it would barely start. Other times, no problems at all.

I started by swapping front and rear relays, no fix. I pulled both fuel pump relays and spread the pins, no fix. Once, while it was stumbling on the driveway, I pulled the rear pump relay…no change with the relay out…put it back in…idle came back up to normal immediately…then back down after 4 seconds. I replaced the rear relay with a new one, but that hasn’t fixed it either. Today, I rewired my fuel pump relays with separate fuses run directly to the battery (common repair/improvement well-documented by a few on this site) just in case, but that hasn’t fixed it either.

Looking for suggestions on next steps to diagnose. I do not have CIS fuel pressure testing equipment. Also, for reference, I am running factory CIS, US fuel system, stock fuel head, Leask WUR. Appreciate any help.

DSPTurtle · 11-13-2011, 04:58 PM

Are you sure both fuel pumps are running? Pull the connector at the metering plate and turn the key to on (not start). Open the front trunk and listen. Get down next to the driver rear tire and listen. Your problem sounds a lot like one I had when my rear fuel pump gave out.
Or... pull the relays one at a time after you have the key turned to on. If there is a change in noise when you pull one of them but not the other, you will know which is working.

Alan L · Alan L's Garage

+1 on that. Sounds like a faulty fuel pump relay - they can be intermittent. Your car will run on one pump, JUST. The fuel pressure is way below optimum.
Alan

oilonly · 11-13-2011, 05:19 PM

There is also a relay under the seat,probably not be the issue just throwing it out there.

mark houghton · 11-13-2011, 05:33 PM

Quote:

Originally Posted by oilonly

There is also a relay under the seat,probably not be the issue just throwing it out there.

Just for the genral wisdom pool, that particular relay under the seat will either (a) allow the car to run normally, or (b) not run at all. Nothing in between...BTDT. It's a $340 piece of crap that an industrious person should wire around.

I'm with the present diagnosis of one fuel pump doing the funky chicken. Besides relays, do check the fuse that feeds both as well as the wiring at the fuse/relay harness for cleanliness and torque on the screws.

Are you running with the O2 sensor or is it bypassed?

As DSPTurtle has recommended, do pull the connector behind the metering plate to force the pumps to run without the engine running....it'll help with the diagnosis. I pulled that connection a long time ago whilst troublshooting something or other (I think it ended up being the relay under the seat) and have never reconnected it. I kinda like hearing the pumps run when I turn on the key....gives me confidence that she'll start.

oilonly · 11-14-2011, 02:30 PM

Quote:

Just for the genral wisdom pool, that particular relay under the seat will either (a) allow the car to run normally, or (b) not run at all. Nothing in between...BTDT. It's a $340 piece of crap that an industrious person should wire around.

Yeah I saw that price also. It's the only relay in my car I haven't changed because of the price. I like the wire around it idea. Will do a search on it.

im4duke · 11-14-2011, 03:40 PM

Thanks for the quick help, guys.

My fuses are new as of last night when I rewired the fuel pump relays separately.

With the key turned to on, I hear the front humming, but no sound from the rear. I swapped the two fuel pump relays and it behaves the same...hum in front, nothing in the rear. I guess after dinner I need to pull the intercooler to get to the plug at the metering plate. Will report back tonight hopefully.

mark houghton · 11-14-2011, 06:37 PM

Quote:

Originally Posted by im4duke

Thanks for the quick help, guys.

My fuses are new as of last night when I rewired the fuel pump relays separately.

With the key turned to on, I hear the front humming, but no sound from the rear. I swapped the two fuel pump relays and it behaves the same...hum in front, nothing in the rear. I guess after dinner I need to pull the intercooler to get to the plug at the metering plate. Will report back tonight hopefully.

Well Max, if your pumps are running (although only one) when you turn on the key, then either your plug at the metering plate is already un-plugged or some previous owner has modified around it. Stock, the pumps should not run with just the key on unless that plug is disconnected. So don't bother pulling the IC (by the way, you can reach the plug without pullling the IC...unless you got mondo fat hands).

im4duke · 11-14-2011, 07:21 PM

Thanks, Mark. I didn't recall seeing it before. Here's a view from the driver's rear looking under the IC. Would it be visible in this view if it was in the stock location?

im4duke · 11-14-2011, 07:32 PM

I think I answered my own question...this picture is from the sticky thread on starting problems. This area is inaccessible on my car without removing the intercooler (kokeln) and the airbox (evoms). I'm going to pull them both anyways so I can see for myself. I don't like not knowing. I think I'll ditch the big airbox and replace it with a round K&N like others have done while I'm at it. That evoms box is a pain to install and actually makes it harder to access the idle adjustment than with the stock box. Look for it in the classifieds soon...

Flying out tomorrow so maybe back at it Saturday. Since the front pump seems to run with the key on, but not the rear, what should I check next?

mark houghton · 11-15-2011, 04:43 AM

Since you've rewired the fuse/relay box and know you have power to at least the rear pump, to narrow things down I would disconnect the wires from the front pump - at the pump - and put a voltmeter on them to assure power is getting down there. Then, to test the pump itself, apply 12V power to it from an external source (run some wire leads direct from a battery) to the pump....see if it runs.

JFairman · 11-15-2011, 05:20 AM

The rear pump is in front of the left rear wheel and wayyy easier to get at than the front pump thats mouted to the front crossmember above a steel skid/splash plate that has to be removed to even see it.
Jack up the back of the car and remove the left rear wheel and the rear one is right there in it's mount alongside the left side longitudinal.

Seeing as the rear pump is the one not working, check for voltage at the wires going to it if you know the rear fuel pump relay is working correctly. If it's getting 12volts than it's worn out, they don't last forever and you need a new one. If it's not getting 12 volts while the front one is it's probably a rear fuel pump relay problem.

The best replacement is a new Bosch motorsport 044 pump and it cost alot less than a new rear 930 pump that doesn't pump as much fuel. You just need to get the fuel inlet line compression fitting adaptor for it. The 2 wire eyelets are a little bigger on the 044 so you change those too. Easy stuff to change.
The 044 checkvalve and banjo fitting outlet is the same as a 930 pump.

im4duke · 11-18-2011, 08:42 PM

Thanks again Mark and Jim.

Removed the intercoooler and airbox tonight. Green plug was in fact connected. I unplugged it and then turned the key on. What a difference in sound. Much more noise/sound from both front and rear. Clearly, before I did this, the slight hum I heard before was not the front fuel pump. They both seem to be making noise.

Didn't have much time to trial and error tonite. Based on the intermittent issue I have experienced with this thing lately, it is possible that the conditions were right tonight anways and things are working 100% for now. I will test again tomorrow and pull relays etc. to see what happens front and rear.

im4duke · 11-22-2011, 06:44 AM

12 volts to both pumps seems fine. They both run with green plug open and key on. They also react correctly to unplugging relays. Any suggestions on what to check next? Does it come down to checking fuel pressures or are there more electrical checks I can perform?

Recall that earlier when it was stumbling at idle on the driveway, I could unplug the rear relay and see no change, but it improved for a second.when I plugged it back in.

wjfk32 · 11-22-2011, 07:57 AM

Try another coil. My coil was ever so slightly leaking....

im4duke · 11-22-2011, 08:40 AM

Quote:

Originally Posted by wjfk32

Try another coil. My coil was ever so slightly leaking....

Thanks, I'm running electromtiove XDi twin plug. I'm pretty sure it isn't spark related.

I'm going to check actual voltage at the rear pump next. Any other electrical tests/checkl points I can verify? Seems like the relay under the seat isn't the problem since the car does run. My fuel pump relay fuses are good and the relays themselves seem to be working.

Alan L · Alan L's Garage

If it running OK now it is going to be hard to diagnose. You probably need to wait til it misbehaves and check by sound/touch/12v, whatever works, that the pumps are both still working. Wonder about then checkingfuel operating pressures, but it is hard to see what could go wacky under these conditions in the WUR. But maybe there is a leaness somewhere . But I would confirm pumps OK under misfire conditions first. If so, maybe time to check system pressures.
Alan

im4duke · 03-21-2012, 06:51 PM

Well...it has been difficult to find time to further diagnose the car. It ran great for about a week, then back to the hesitation and stumbling. Parked it and was planning to check voltage to the fuel pumps at idle as next step. When I started it recently to back out of the garage so I didn't gas myself, the idle began fluctuating up then down. I shot a 1 minute video of this which it now does consistently on startup.

IMG_0055.MOV - YouTube

After about 1 minute, it settles into a decent idle, but I have not driven out of the garage at this point. To be clear, my foot is on the clutch in the video and I don't touch anything else. Does the behavior in the video suggest any particular component(s) or issues? I am less convinced that my rear pump is failing or that it has anything to do with my fuel pump relays or fuses. Richard Clewett said it did not seem like anything realted to the XDi system based on his experience. Open to all suggestions. Anyone in DFW have CIS test equipment and care to lend a hand?

im4duke · 03-21-2012, 07:38 PM

Quote:

Try another coil. My coil was ever so slightly leaking....

Just saw this. No coil, running electromotive XDi twin plug.

icemann427 · 05:54 AM

If you think it is fuel related, go ahead and replace your fuel filter. Fuel filter is a 3"x5" canister along the left side engine compartment wall with a fuel fitting/hose at the top and bottom. I replaced mine a couple of times with related problems and it took care of it.