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Turbofrog
 
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Join Date: Aug 2009
Location: Europe
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AFR jumps to rich on light cruise?

This just happened to me and it's the first time. also the rpms on idle jumped to 1200 from 800. AFR jumped from 14.7 to around 13 and idle from 14 to 12?

My thoughts for the reason are.

1. Some hose started to leak or unplugged
2. Cold start injector leak
3. My supposedly defective front pump started to function

What else could it be?

Wur is warm so I don't think it can go to cold start control pressure unless elec problem so
4. Wur does not get power and goes to cold control pressure


EDIT:
When I started it again after 30min the rpms were even higher at 1600 rpm and still very rich overall. Turning the rpm screw all the way closed did not help so there must be a leak after the throttle body, right? Are there any vacuum connections there?

I had to dial the warm control pressure and idle CO leaner and now it seems fine except high idle.

Very odd situation.

Last edited by smurfbus; 06-19-2010 at 03:04 AM.. Reason: more info
Old 06-19-2010, 12:55 AM
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I had a similar situation with the hot idle AFR going rich like around 12:1 and idle speed going high out of the blue a couple months ago.
Turned out the rear fuel pump relay coil windings took went bad and the car was running on the front fuel pump only.

The WUR and AAV heater elements also get their power from the rear fuel pump relay so they stayed cold and acted like the motor was on a real long cold start.

Put in a new relay and everything went back to normal.
Old 06-19-2010, 08:03 AM
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Turbofrog
 
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Wow, newer thought they relayed those together. I wonder if the 044 at the rear will keep blowing the rear relay? Now I kinda hope the front pump is bad so a good one will help the rear 044 so it does not have to work so hard.

Did you try to lower the idle rpms with the rpm screw? Sound strage that the rpms can't be lower with it.

I did notice wot was getting even leaner than usual so if the rear one is not functional the front one does work as it was not that bad.

Thanks
Old 06-19-2010, 09:21 AM
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"Did you try to lower the idle rpms with the rpm screw?"
No I didn't lower the idle speed screw because I knew something was wrong, I know 930 CIS as well as anyone now, and my idle speed is usually right where I want it (800rpms) and readjusting the idle speed around whatever went wrong makes no sense.

"Sound strage that the rpms can't be lower with it."
Thats because the cold start AAV vave is bypassing air around the throttle butterfly all the time as long as it isn't really heat soaked by a hot engine or getting 12 volts to heat up the bimetallic spring inside and close it... lowering the idle speed.

I have a DPDT switch hidden in the car that takes fused battery power in 2 seperate 12 gauge leads through the 2 seperate poles of the DPDT switch to keep the 2 seperate fuel pumps power leads isolated, one lead for each fuel pump. If you don't isolate the wires when doing that you'll permanently bridge the power supply lines from the relays to the fuel pumps together and thats not good for the 2 seperate fuel pump relays.
It bypasses the 2 fuel pump relays so I can turn both fuel pumps on without any of the multiple relays in the fuel pump cicuit used or involved.

When I noticed the weird rich AFR's and high idle speed I tried flipping that swtch and sure enough the AFR's slowly went to mormal and the idle speed dropped because now the rear fiuel pump and the WUR and AAV heater elements were getting power.
To make sure that was it I turned the switch back off and the AFR'S started slowly going richer and the idle speed at stop lights and signs creeped back up.

I had only been driving around 5 minutes when all this happened so the motor wasn't hot enough to heat soak the WUR or AAV yet and they completely rely on the heater elements to warm up after a cold start.

I put the DPDT fuel pump relay bypass switch in because my fuel pumps used to shut off randomly out of the blue every now and then and strand me on the side of the road or in the mioddle of an intersection until they would decide to work again...
That REALLY sucks and is very dangerous.
Turned out to be an intermittant plug/pin conection to the "speed relay" or factory rev limiter relay under the driver seat.
Old 06-19-2010, 09:52 AM
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Turbofrog
 
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Nice work around. I'm not capable of doing stuff like that. I think the sound of the front pump changed some after I installed the 044 on the rear. I might try one spare relay before I try to install a another pump for the front. I got 3 or 4 spare red relays with the car.

Thanks again
Old 06-19-2010, 11:02 AM
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You should connect an ammeter across the pins you would jump in the red relay sockets to see how much current each fuel pump is drawing while it runs.
Jump pins 87 and 30 on a red relay socket with an ammeter set to the 30 amp setting to make a pump run and check amperage draw of the fuel pump. The pin numbers are on the bottom of a red relay next to the pins.

Do not ever jump those same pins on the yellow relay socket in the rear of the car or you'll melt wire insulation from the socket and see smoke come from under the relay panel... BTDT.
To check or jump the yellow relay socket you jump socket pins 87a and 86 and the pin location markings are on the side of my 1987 yellow relay, not on the bottom. The yellow relay for a 1987 does not have the brown wire coming out of the side. I don't know what yours is like.

Check them individually while only the pump being tested is running and again while the other pump is running too for a current draw comparison.

You'll probably see the 044 is doing most of the work and drawing more amperage or current than the front pump because it's a bigger and higher flow pump. On top of that you said your front pump has no identifcation markings in an earlier post and that usually means it's a chinese fake bosch fuel pump.

That would be in check with the front pump sounding quieter now while the 044 in the rear is running.
Old 06-19-2010, 11:35 AM
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Turbofrog
 
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Will try those tests later. No yellow relay on the rear on mine and the pumps run when ignition on.

EDIT: The front pump seems to have some pressed marks on it like bosch and numbers. The rear did not have any markings to be seen.

EDIT:2 The 35A Fuse for the 044 had blown! The car has two separate fuses for the fuel pumps and the lid says 2*25A but the blown one was 35A. I replaced with a 30A one which I happened to find. The wires looked ok.

I could not get any measurement I would understand. The pump would not fire when the 40amp gauge was in the 78 and 30 ports and the amp showed about 11A for both pumps when the relays where not in there.

Both pumps strugled without the other one? The 044 alone would not start first at all but started to pump but barely. The front only made stroke like noises but would pump better when 044 was pumping.

I still think changing the front would help but that would mean emptying the tank and I was not up to that yet. Is it easiest to open tha large allen bolt at hte bottom of the tank or just remove the pump line?

Last edited by smurfbus; 06-20-2010 at 08:01 AM..
Old 06-19-2010, 03:52 PM
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Turbofrog
 
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Oh cheisse, now after putting it back to ground the engine started to sound horrible with bad mechanical clanking. No noises when I came home the day the richness happened. It sounds a bit like power steering without enough fluid? What could that be? AFR was ok at 14 but the start up was not so rich as it probably should have been. It was up to 14AF pretty soon.

Broken rocker or suddenly lost valve/rocker adjustment? It could be major trouble too but the engine was rebuild so I really hope not.
Old 06-20-2010, 09:35 AM
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sounds like problems are beyond guessing at a distance now and maybe getting worse...

hopefully somone that knows these cars can listen to it for you or posting a sound/video clip from a digital camera on you tube with a link here might help
Old 06-20-2010, 10:44 AM
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Turbofrog
 
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The noise was predetonation I think

Took the IC out and the distributor seemed loose and after some painfull reaching got it to seat well. The rear clip on the dist. is PITA to get on. The fuel line fidling (when I installed the rear 044) must have popped the rear clip loose.

I now have two 044 pumps so fuel supply should be enough unless there are other problems in wiring or FD. I hope to get her logged next week.

How does the front fuel pump relay power the AAV? The wiring diagram on the workshop pdf are so messy I can't follow them. I saw a pic here that had descriptions of the plugs in the relay and none of them was to AAV. IIRC two went to CDI and 78 to pump, 30 being always hot.

Did you mean the pumps should have run when I had my 40A gauge at the 30 and 78 plugs? Nothing happened, maybe the contact was not enough?

Last edited by smurfbus; 06-22-2010 at 09:01 PM..
Old 06-22-2010, 08:58 PM
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