LH CONTROL UNIT- help

[bluemane500]

I'M HOPING SOMEONE COULD HELP ME, i swapped an engine in my 85 and Ive been trying to start it but there is no spark and the fuel pump wont come on. i have power to the ignition coils power at (30)-(15) to all relays but pin #21 in the LH control unit will not ground (energize) relay for fuel pump, i get intermittent half second energizing for fuel relay sometimes it will cycle , sometimes it wont. this car was running fine last month until it snapped a cam and bent some valves, so computers were working fine, i don't know what direction to go?

[Landseer]

Where did you ground the engine harness segment that is associated with the LH computer?

(A series of grounds attach on the left and right sides of the back of the engine, at the edges of the valley. These are associated with all the critical engine sensors and computers)
(And, the ground strap from engine to frame rail must be in-place)

[bluemane500]

all grounds are in tact the harness has two grounds at the rear of the engine on either sides of the speed reference sensor and the engine ground is also in tact

[Mrmerlin]

are the gounds connected above the Ce panel?
Did you swap out the 4 relays for starting.
Must use new relays

[Landseer]

Is alarm deactivated?
Is each female terminal of the W-plug seated in the CE panel on its male end?

Here's some more troubleshooting for 85 USA.

[Landseer]

Here's some more. Note the factory manual error and correction.
Not sure what documentation you have, BTW.

You might want to jumper the three important relays in various combinations with each other as another troubleshooting step. New relays for these three!



If this doesn't help, go back and recheck the valley grounds. Its not unheard-of for corrosion to affect the joint where the wires enter the ring terminals.

I'd also consider changing the battery ground strap. We've seen them take-out the 32V cars, and yes, I did read how the car was running when the valves crashed

[bluemane500]

well i didnt use new relays all relays are working fine, the pump will run if i close the contacts but still, there is no spark,but power at coils,i feel as if ground is missing from the harness wires to control computer. they are bolted to engine, where would pin#21 get its ground to energize fuel relay? thats the question

[bluemane500]

i once had a 911 that i color changed and painted everthing ,after everything worked slower than normal and the charging system would not put out enough volts , even with high output alternator, painted complete engine also,after many man hours of tracking wiring i ran a heavy ground cable from the alternator housing after grinding all paint off to the body,, and that helped it but not completely restored power,then i went directly to the battery and wah la , the thirty year old car had lost its ability to carry a proper ground

[bluemane500]

and mrmerlin , why must i use new relays?

[Landseer]

Pin 21 doesn't even connect to the fuel pump relay.
New relays because they get dodgy, especially after sitting.

You seem to know an awful lot. That isn't accurate nor working for you.

YOYO
(your on your own)

[Pete R]

In addition to the previous qualified advise, my total guess (I am not familar with your injection) , is that something is still not hooked up. I'd recheck all the connections you had to break to make the motor swap, maybe one of the connectors isn't quite snapped in all the way. Is this one of those systems that if it doesnt see spark it won't send the fuel?

[Landseer]

That could be the CPS, which Wally just noted on rennlist.
Good logic Pete.

[bluemane500]

YOYO? im not a mechanic im a bodyman,, i swapped the motor but couldnt start it so i called in help, he told me pi 21 wouldnt energize fuel relay but didnt know why so thats why i posted the topic, im trying to get my car running. i dont know if 21 is related to fuel pump but i didnt know i was own my own, i thought this was a site to get help, i dont know an awful lot but i do know im not own my own, maybe the guy made a mistake,, maybe not

[Mrmerlin]

would you rather use 25 YO relays for the engine computer/pump/ignition to work??

If you washed the engine compartment with the engine removed,
then there is a good chance the CE panel got wet i would also reclean all of the fuses,
and check the relays for corroded pins any relay with corroded pins should be opened and the contacts checked

Also inspect the hot posty connection and the 14 pin connector above it ,
open the top half of the connector and see if there is any shedding insulation

[stepson]

Checck the model number on your LH and EZK computers. Post the numbers here so somebody can verify that you have the correct computers. Did you swap in an '85 engine?
Do you have power at your coils?

When my '84 Euro LH was bad, the car would not start, but the LH would not energize the fuel pump relay. Sent it off to be repaired and all was good.

Is there anyone close to you that could try your computers in their car?

[Landseer]

Originally Posted by bluemane500

YOYO? im not a mechanic im a bodyman,, i swapped the motor but couldnt start it so i called in help, he told me pi 21 wouldnt energize fuel relay but didnt know why so thats why i posted the topic, im trying to get my car running. i dont know if 21 is related to fuel pump but i didnt know i was own my own, i thought this was a site to get help, i dont know an awful lot but i do know im not own my own, maybe the guy made a mistake,, maybe not

Your level of questioning, on the surface, made it seem you had electrical knowledge and were working from wiring diagrams. You used such tone and insistence that I had to go back and review them myself which revealed you had been given wrong advice.

The things that disrupt the signal are often intermittent and include relays, dirty contacts, ignition switch, ground cables, ground connections, melts behind the panel, alarm set, brain problem and CPS (likely since it was touched, along with grounds). That a car was running before it went down is often a red herring. Between the two boards you got that advice virtually instantly and for free from some of the more knowledgeable enthusiasts in the country specific to the S3 cars . Half of it is still going over your head, though.

You must be a minimalistic patcher to challenge a recommendation to change a set of $5 relays. That's ok.
The reason for the advice, and the advice on all the electrical contact cleaning, is that on this era of automobiles, and this car in particular, the electrical effects of the sum of resistances across the circuit seem to shut the cars down. Especially when a little water is involved and most of the cars we see have a little water ingress. By cleaning each junction, whether they look like they need it or not, a number of us deep hobbyists have been able to renew the reliability.

First step on one of these is complete removal, polishing and refusing of the panel, replacing all top row and critical running relays.


BTW, what bodywork boards do you recommend for advice? Are you contributing your expertise? I could use some help.

[harborman]

The relays can stick or not operate. Had it happen on my fog light relay. Even after I took it apart to investigate and clean the contacts, it stuck again. I replaced ALL # 53 relays in my car and have not had a problem since. They are very cheap, $5 or so. You need to clean that fuse panel as was mentioned. My car is about as clean as they get for a 86, almost new condition but 25 years old, so even with that, you need to clean all the electronics connections. Good luck!

Also, one thing, even though my car sat garaged, seldom driven for 19 years, some indicator lights did not work. As I drove the car, more things began to work and became more reliable.

[MPDano]

That reminds me of a great Yoyo Video i must share

[harborman]

MPDano, could you do the "walk the dog" with yours??? Hi hi...

[Pete R]

Mpdano, second best yoyo vid I've seen. #1 was x rated and had a great ping pong ball finaly