This is great.. Replaced rear main seal and now engine will not start and stay running. Symptom is similar to vacuum leak (major) like if you remove the oil filler cap while it's running. 1. All electrical connections and vacuum connections are connected and seem to be good. I didn't drop engine to replace the seal, I just removed transmission and replaced from bottom so can't figure out this problem. I did remove the S-tube from mass air sensor to butterfly and have had it off 5 more times since this started checking for cracks and such. ll is good there. It acts like if you forget to plug the air flow sensor cable on and then try to start, runs for 1/2 second then dies. Checked all injectors and all are firing. Checked resistor pack, good, double relay picking and good. Have fuel to the rails and good pressure. metered cable from air sensor to ecu and all good. So why won't this engine run. Any help would be appreciated.

When it starts for a sec then dies, it can be caused from the circuit that runs from the dual relay to the AFM and back.
First thing I would be checking would be whether the dual relay is firmly attached at the base and all wires are making contact with the spade connectors. If they make good contact, pull the dual relay and test it. See: http://www.914club.com/bbs2/index.php?showtopic=235816

for the three tests. Your problem sounds like a failure of the third test.

Tell us the results, if the dual relay passes all three tests, we'll move to the AFM

OK, I tried the tests from the link. From neg of 9v battery on 86, none of the test work as indicated but with neg on 85 all the test work as such. With the cover removed from dual relay and installed in car, when tool wench tries to start relay from white/ecu cable picks when key on and relay from black shielded cable picks and fuel pump relay runs. Look like it should be working.. I just looked at the pictures from test#1, 2, and 3. The negative lead is located on what my relay shows as position 85, not 86??? My relay looks a little differently than the one in the picture, mine is vw pn# 022 906 059 and bosch 3 0332 514 104. Also, I have a spare good AFM that I tried and acts exactly the same way.

My mistake. The neg is 85.The vw part o22 906 059 works the same. I have tested both.

When the key is initially turned on, 12v goes from 88a to the AFM; when the engine begins to start and the flapper inside the AFM opens, the 12v at the AFM returns to 86b of the dual relay, which in turn allows 88d--the fuel pump wire- to get 12v

I would test 86b for 12. Set up the meter to read 86b, turn on the key, then open the flapper inside the AFM. If you get 12v, then dual relay and AFM are working properly

Looks like the 12v is there and I can hear the fuel pump run. Seems a bit like an open vacuum system failure. If the main seal is not sufficiantly holding back the pressure in the case/system would the symptom be a bit like what you would get if you removed the oil filler cap? Main seal I put in was old one, but thought was good, didn't have a new one but just a thought.

Don't know the answer to the main seal. Someone may chime in on that. At least you have eliminated the dual relay and AFM.

hi, i would make sure the ground cable connecting the transmition to the chasis is connected.

Thanks for the update but I have the braided cable installed and also another braided cable installed from transmission to frame in a different place also, extra current carrying capacity. I am going after the main seal next since it is really leaking, my motto has been to fix the obvious things first, often times that takes care of the problem, We shall see..

Seems like a fuel line pressure problem from the tank into the fuel pump. Check there is fuel pressure into the fuel pump and also the return fuel line hose back to the fuel tank is not clogging.

MikeCool

...If it did'nt do it before??....go back over
what you did! and try again
(make sure everything is buttoned down tight) Ljet is vaccum sensitive

Ok, got this one fixed. I pulled back boot on connector from AFM to ECU and found good metered wire broken and touching pin, when I metered for continuity must have flexed it just right and was sent down the river. I will now continue to replaced main seal for oil leak.. again...3rd time is the charm. Thanks for all who helped and chimed in on this bug.

Good News ! Are you saying the connection from the AFM to 86b on the dual relay was broken, ( like a test # 3 failure) or a wire from the ECU harness ? Just want to better understand, since I have L-Jet as well.

The cable connector from the AFM that has 6 wire connector. Pulled boot back and pin#7 wire had broken away from pin, this wire goes to ECU main connector, when I metered connection to ECU I must have flexed it just right so it was touching the pin, so when cable was installed must not have been making. Take your cable from the AFM and unplug it, now try and start the car, will start for a second and die. That was my symptom.

Thanks, this is one symptom/resolution for the big brain to remember!