Help diagnosing weird FI problem

[tomp]

I need some help diagnosing a bosch L-jet problem that developed last weekend on the Houston MSR track. I had four good sessions on saturday. Sunday I had a good 1st session but noticed a couple of brief cutouts down a straight. On the 3rd session the car almost didnt start and wouldnt take throttle. It bucked and jumped and seemed as if the rev limited was cutting in at weird rpms. I got it home did some checks but havent found a problem.
Fuel pressure is 36 lbs, strong spark, Tried new plugs. Temp sensor 350 ohms hot. Check connections are solid to everything including the ecu. Swapped another air meter. Nothing. Problem remains. Perhaps I damaged the ECU by repeatedly hammering the rev limiter. There were a couple of places where it was faster to just stay on the limiter that shift up and back down. Any suggestions on what to check next?
-Tom P.
BTW: The milano did extremly well last weekend. I have to get this fixed so it can defend its honour at the next event!

[jontg428]

Replace the fuel filter, you can still have good fuel preassure with a plugged filter, I had this happen on my 164, I think its more a fuel volume issue in that case. Also, check the fuel pump screen for blockages as well. Also, any major vacume leaks, maybe cracked intake boot, or some other intake line? Hitting the rev limiter should not damage the ecu I would think, so its got to be something else. I have never owned a milano, but I hope that helps, good luck,
Jon

[tomp]

Good suggestions.Thats what I was thinking too so I hooked up a fuel pressure gage and hung it out of the hood so it could be watch while driving. It I drove up the street and pressure was between 30 and 37 lbs depending on throttle position.That test makes me think the problem lies elsewhere. Also, I noted it took several hours for the pressure to drop down to 20lbs. I am planning on replacing the filter and cleaning the screen anyway though.
................
Update: I belive I may have found the problem. The ground wires under the valve cover bolt are loose. The bolt in fact seems to be stripped. I tightend it up as best I could and it fired right up. I do further checks after work and post it here for future reference.

-Tom P.

[nikosd]

Had a similar problem.
1st thing I thought was the throttle and potentiometer. It was ok.
2nd thing to think about was fuel pump. Was ok too.

It happen to be a cut/short circuit/ground wire in the between the L-jet and the engine. That thing also gave me the christmas tree effect sometimes in the ARC.

Good luck holding up the Milano/75 honour in track !

Nick

[slyalfa]

are you reading the pressure on the rail after the regulator?
but I had the hall amp (the part under the coil) fail and it would run and stop and run. I found it by flexing the connector going to it, and that made it better/worse
I grabed one off a VW at the junk yard.

[tomp]

Yep, tee-ed into the line between the "dashpot and main fuel line. You know, you can feel a small pulse each time the injectors fire. They are bank fired in the L-jet. I snugged up the grounds and it now passes the driveway test. Ill take it for a short spin later this evening. Ill have to get a 7x1.0 helicoil kit to fix the stripped bolt holes.

[Meimaridis]

Another similar problem, in a 75 2.0 TS. Usually when the car gets hot and the cooling fan takes action, the engine seems to choke, cuts rpm and doesn't rev higher than 4 or 5.000rpm... Sometimes even cant hold idle and stops...

Once in cold start, it increased idle instantly and then had unstable idle for a couple of seconds and then stopped...

My reliable (thank god) mechanic said about faulty MAF sensor. Does anyone had same problems?

[tomp]

That sounds pretty bizzare. What kind of MAF meter does that car have?

[Meimaridis]

Bosch (damn germans) serial number 0280202202 and its very expensive. Costs about 700 euros as new and it's the same part used in 164 and some spiders... I also found reconditioned in www.bba-reman.com with 180 euros...

[tomp]

Quote:

Originally Posted by Meimaridis Bosch (damn germans) serial number 0280202202 and its very expensive. Costs about 700 euros as new and it's the same part used in 164 and some spiders... I also found reconditioned in www.bba-reman.com with 180 euros...

[Greg Gordon]

tomp, this sounds like an ECU ground problem. I would look at all the grounds in the system, but start with the ECU ground since this can cause your exact problem.

Greg
www.hiperformancestore.com

[tomp]

Yep, thats exactly what it was. Im this case the bolt on the rear righhand valve cover was stripped and was not clamping the ground wires reliably. Heli-Coiled it and all is well again. I can believe I forgot to check that!
-Tom.

[Greg Gordon]

Great, I am glad it's fixed.
Greg
www.hiperformancestore.com