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-   -   930 Suddenly Going Lean (http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/818414-930-suddenly-going-lean.html)

ObrHaus 06-29-2014 06:06 AM

930 Suddenly Going Lean
 
I just got done putting new torsion bars and rebel rsr mounts in yesterday and went for a drive on our very wonderful Nova Scotian back roads. On the way home I was accelerating in second gear, got on to boost and then the engine stumbled and fell on its face, seemed that I could keep driving without problem off of boost no matter the rpm. I made a few more attempts to get on boost and noted I was going lean around ~3900 rpm afr 13, and increasing drastically with rpm. I tried a few more things, thought maybe I was sucking air in between the metering plate and turbo but I could hit 1 bar at 3000 rpm and hold 11 afr steady to 3700 rpm.

Once home I left it idling in the driveway, pulled fuel pump relay 1 and the car kept idling fine, pulled relay 2 and it kind of bogged down and stalled slowly, I flipped the relays around to test them and same result, except it just bogged down a little but didn't stall this time. I then saw the fuse for the pumps was discolored and hot to the touch, I replaced it hoping it was my problem, no luck.

I'm thinking with the recent hot weather here I may have a weak fuel pump, anyone care to share their thoughts?

oilonly 06-29-2014 10:04 AM

I say you need to use a fuse for each pump, open up the prongs on those red relays a bit using a fine blade and take for ride again see if any improvement.

http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/575052-930-fuel-pump-fuse-overload-solution.html

Tt surgeon 06-29-2014 12:31 PM

I think one of your fuel pumps is on the way out, two fuses is a great idea.
Al, once I get mine back home you gotta come over and help me dual fuse the sob.
C

Hams930T 06-29-2014 12:42 PM

I know the deviates from the original wiring; but I decided to bypass the original relay wiring and run dedicated 40amp relays to each of the fuel pumps. I used the output wire from my front pump as my switched +12v signal to the relays so they will operate as intended, not just under key power. By doing this, I am getting a very clean signal to my fuel pumps. I basically purchased the 40amp fuel pump kits from Painless Wiring Products. The wiring is 12awg to the relay and then 12awg out to each pump. I have a 30amp blade fuse inline from the battery to the relay. And like I said, the +12v switched power is the actual power wire from the original front fuel pump - so my original relays are essentially under no load now.

I would consider this mod and likely change your fuel pumps.

Best of luck.

Chris.

T77911S 06-30-2014 02:59 AM

here is what i did. the benefit is that it looks original and no wire splicing.
there is a wire that connects pin 30 of the 2 relays. cut that wire very close to the first relay. i had a spare fuse since i dont have fog lights so i ran that wire to the bottom of that fuse socoket. (after removing the other wires to it). then i ran a larger red wire from the top of the oroginal fuel pump to the top of the new second fuel pump fuse.
the trickiest part is cutting the correct wire between the 2 relays.

6771911esses 06-30-2014 03:41 AM

You may have a fuel pump that is starting to die or full of crud and pulling a lot of juice hence the discolored fuse.

ObrHaus 06-30-2014 04:16 AM

Thanks guys, once I get the car running right again I will do the fuse mod but I don't want to compound my problem before I find the issue. What kind of amperage should I be drawing from each fuel pump? It has gotten worse, I can't even go on boost now without going lean.

6771911esses 06-30-2014 04:19 AM

Upgrading your fuse will not repair a dying pump. I would start by removing the faulty pump and bench testing it. Replace IMO and run the factory recommended fuse. Electric motors age too.

T77911S 06-30-2014 04:20 AM

around 6-7 amps.

i thought you narrowed it down to the FP.

check the WUR diaphragm and the vac hose going to it. that was the first thing i thought of when you said you were lean on boost.
another thing is the rubber boot between the AFM and turbo. if that is soft it will collapse under boost

Miguel Antonett 06-30-2014 04:28 AM

If you have CIS, the first thing I'd check is the WUR.

6771911esses 06-30-2014 05:36 AM

overheating fuse can only be the fuel pomp binding or stuck. the rest of the suggestions are good but should not influence your findings with the fuse.

heliolps2 06-30-2014 06:07 AM

if it were a fuel pump issue . the engine would run rich, because of the low pressure,

just athought

heliolps2 06-30-2014 06:15 AM

I would start with making sure all spark wires are plugged in all the way, all so check for vacuum line leaks, recheck your spark plug gap, if the gap is to big you could experience blow out when the boost comes on,

ObrHaus 06-30-2014 09:47 PM

Both pumps drawing 6 amps. The rubber tube that connects to the inlet of the turbo is soft and cracking around the edges. I've ordered a replacement. Thanks a lot for the suggestions I will look into them when I get home.

rrental 07-01-2014 06:56 AM

What you are describing sounds to me like one of your fuel pumps is not working. Had the exact same problem last year. All is good until boost. Check both your relays in the front. I replaced the fuel pump but that was not the problem.

Both Relays where fine, and I replaced the pump and the problem was still there. At the end is was a bad connection on the fuse box ( the rubber connector where the relay goes in)

Consequently, if your pump is bad I have still a good one on the shelf here!

fredmeister 07-01-2014 07:59 AM

Quote:

Originally Posted by rrental (Post 8143235)
What you are describing sounds to me like one of your fuel pumps is not working. Had the exact same problem last year. All is good until boost. Check both your relays in the front. I replaced the fuel pump but that was not the problem.

Both Relays where fine, and I replaced the pump and the problem was still there. At the end is was a bad connection on the fuse box ( the rubber connector where the relay goes in)

Consequently, if your pump is bad I have still a good one on the shelf here!

How did you repair the rubber connector or did you just replace them with new?

They are $$ little items here on hosts parts page.

thanks,
Fred

rrental 07-05-2014 04:15 PM

Quote:

Originally Posted by fredmeister (Post 8143378)
How did you repair the rubber connector or did you just replace them with new?

They are $$ little items here on hosts parts page.

thanks,
Fred

Put them in line again with a sharp object and cleaned with Wurth electric cleaner. No problems since.

ObrHaus 07-11-2014 04:24 PM

An update, today I replaced both fuel pumps, fuel filter, fuel pump relays, turbo silicone intake coupler ( old one was cracked ) and I'm still getting the same issue. Actually after putting around with the car it has gotten worse, now wants to go lean if you rev it at all. In the driveway I held the motor @ 3600 rpm, my afr was around 14, which is fine but if there was any load it would be higher, I had a friend push my metering plate down slightly, it richens up the way it should. Now i'm thinking I have a suction leak somewhere between the metering plate and intake )after the intercooler), but I've checked everywhere and its getting frustrating.

Any ideas?

pkracer21j 07-11-2014 04:38 PM

spray some spray start around the injector blocks...they're notorious for cracking.
check the torque on the intake manifold bolts as well.
check the o ring that goes around the throttle body, those can occasionally pop out of place under boost.

mooney265 07-11-2014 04:55 PM

I didn't see anything about your WUR.

1. Do you have an adjustable WUR?
2. Have you checked the CP's? Boost CP? Do you have CIS Gauges?
3. Did you log your last CP readings and have they changed?

Maybe something is going on there? That's easier than looking for a leak IMO...


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