Johnu33301

N882928 Did you check the voltage from the injector wire, thats my problem I have no juice and I think its a wiring problem. I'm hoping that it is the same problem you have so I can get this thing back on the road its been down for awhile and I have changed everything !!! Relays, Regulators all three and even the L-Jet brain which I found out was good!! so now I have an extra.. Oh and I also had the injectors cleaned and pressure checked and replaced the ICU! I'm starting to wonder from Mikes post about the cold start valve.

N882928

I think Mike mentioned the Aux. Air valve which is different than the Cold Start Valve which is the extra fuel injector that fires on fisrt crank to give the engine gas to start. It runs of the battery and not the brain. I think this is why my car runs for a sec. after that gas is used the car will die unless the gas from the injectors is ignited. The Aux. air valve is a valve that I believe bypasses the AFM or flapper valve as some call it to give the car more air at idle once the car warms up a temp circut closes the Aux. air valve. Anyone please correct me if I'm wrong. However if you do not have any juice to the injector wires that is a problem I would start with first. Could it be a bad injection ground? I have checked most of mine already but have one or two more to go.

Johnu33301

Where do I start to find the grounds?

N882928

Johnu

The gounds I hear that are the most problematic (clean cor. etc.):

1. Between engine block and body, under car, pass side, where Y pipe connects on that side.
2. Pass side, jumper terminal front, engine compartment. Unscrew terminal to get at ground wire.
3. Pass side, camshaft housing around cyl. 2 mounted to metal air tube.
4. Pass side, camshaft housing, same air tube father rear under blowoff switch valve.

Start with those. The car has other grounds but these seem to be most problematic.

Johnu33301

Thanks N8 and Jack, I'll check those out tomorrow and clean the grounds, do you all know what purpose the green wire is that goes to the distribitor and connects to the ICU?

Johnu33301

Hey Jack just checked the two 87 terminals are they the right side and middle? My middle has no metal prong it it to jump am I looking at the correct thing? When I looked at the relay it does have stamped on the outside of it 2 87 terminals?????

Marc Schwager

Guys, just to narrow your search space, for the L jet there are 2 items that effect cold start and one that is frankly pretty useless. I don't think any of them would cause your problems.

1) Cold start injector - Pumps a bit of extra gas into the system for a few seconds on start up. If this doesn't work it's hard to start but once started should keep running fine. This is at the back of the engine on the pass. side. Easily tested per the WSM

2) The aux air valve - This valve starts open and slowly closes due to electrical heating of a bi-metal strip. It helps the car run better until it warms up. It is easy to pull and test with either a 12v source or by putting it into the feezer and warming it up in an oven - look through and see if the valve opens and then closes. It is in front of the cold start injector on the pass side.

3) The vacuum limiter - this was removed from the cars after around 84. It's shown in Rich's post as item number 29. It only controls how the idle settles in when you drop off the throttle fast.

Since you guys are both new to the forum, let me just mention if you haven't read the "new visitor" post you should do so. It has links to excellent troubleshooting procedures (nichols et al) and how to get a CD copy of the workshop manuals which are IMHO crucial for tracing electrical problems.

Good luck

Rich9928p

There is only one socket 87 for the AFC relay. As you see from the schematics, the battery voltage comes in via circuit 30 and then goes to the fuel injectors. The L-Jetronic provides the switch between the fuel injectors and ground.

So you need to
a. confirm that 12V (nominal battery voltage) is at AFC socket pin 30
b. bridge AFC relay socket 30 and 87
c. measure voltage at the fuel injectors
c1. if there is 12 V at the injectors, go to d. If there is not 12V at the fuel injectors, inspect the wiring and repair the open circuit
d. check the circuits between the fuel injectors and the L-Jet connector. To do this, you will need to disconnect the connectors from the fuel injectors and test the resistance between the ground side (NO 12 V when AFC relay jumpered) and L-Jet connector pins 32 and 33 (depending upon which cylinder(s)). If the resistance is low then you know the current path from the fuel injector to the L-Jetronic is good.
e. inspect the current path from the L-Jetronic to ground. Measure the resistance from L-Jet connector pins 5, 16,17 and 35 and a good chassis ground. If all these circuits have low resistance then the return to ground path is good.

If all of these are good, then the L-Jetronic fuel injection controller could be bad or other systems could be bad.

FYI, the L-Jetronic pin 1 gets the engine rotation information from the TZS spark box pin 16. The TZS spark box gets the rotation information from the Hall-effect sensor in the distributor via pin 7. The so-called "green wire" is a shielded cable from the Hall-effect sensor to the TZS spark box, shielding is pin 31d . So you need to also inspect that circuit to ensure the engine rotation pulses are getting to the L-Jetronic controller.

Johnu33301

Jack!!!!!! You are the man this car has been off the road for a year, I jumpered with the wire and it frickin started !!!!!!!!!!!!!!!!!!!!!!!!!!! The new relay that I had in there must have been bad!!!! Ok if you are ever in Cincinnati look up the nearest Air Force Recruiter for Nursing (That would be me) and we will go out for some cold Amstel !!!!!!!!!!! Now after it warmed up it started to smoke from the Pas side engine under the head. I think its from old oil burning off. Anyone ever have that problem...

Jack Thanks again!!!!!!!!!! and everyone else for all your tips ......................

John Underwood

Rich9928p

John,

It is time for a beer, any running 928 is reason for that!

But, if a replacement AFC relay doesn't fix your problem there may not be the switching current going to the AFC relay to turn it on. If you find that is the fact, then you work backwards from the 15 bus.

Mike LaBranche

I can also happily report the return of the BWAAHHH. My problem was grounds. Tried the AFC jumper... no joy. Cleaned up nasty grounds at battery lead connection to frame, jump post in the bay, engine to frame. Beast fires up immediately now, nice smooth idle with the fresh squirters and electrical gremlin exorcised. Congrats to all that have returned to normal health.

Mike
84 S
78 OB

AO

Wow! Fixed 2 sharks with one thread. Impressive.

N882928

Make that 3 sharks back on the road! I ordered a new OE Porsche AFC relay just for kicks, popped it in and she fired right up on the first crank. Happy but confused...The first thing I replaced was this relay but it was with an aftermarket relay. I also tested the relay connections but as described in the manuals and not with the third connection as Jack described. So the manuals are wrong and I got a bum relay? Or is there something special about the Porsche relay? Anyway thanks to all for the help. I guess I should celebrate but this had me perplexed for a while. Good grief!

flyinglynx

Ground points, ground points, ground points. Had this same start-die problem just after cleaning the injectors, just like someone else in this post. At some point I was under the hood with the ignition on and when I moved the injector leads, I heard them all fire simultaneously. It was that ground point on the right cam-housing. Now I'm an hour late for work, but at least I'll arrive in style.

jwarner6

Check mine off as another shark resurected by installing the correct Fuel Injection Relay! Thank you all so so much.