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1980 manual won't start

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Old 03-20-2024 | 06:50 PM
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Default 1980 manual won't start

car has been a little finicky to start over the last three weeks, only on three occasions. Cold start little slow in catching on today but once started ran fine to work 30 miles. Started as normal when leaving work. stopped at a service station close to home and would not start after stopping. Pumping accelerator no help. Turns over fine. had some one turn the ignition key on while I listened to fuel pump under the car, whines for a couple of seconds then stops (which I think is normal, and eliminates the fuel relay and fuel pump not working). car was running fine and no warning lights. any ideas. About to drive back to my car with some tools and relays/fuses. car has been a daily driver for the last four months and has had high pressure fuel lines replaced and injectors removed and cleaned prior to the last four months. Grounds have been cleaned/ replaced over the last year. No recent work. thanks for any advice..david

Last edited by NAVYEOD; 03-20-2024 at 06:52 PM.
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Old 03-20-2024 | 07:06 PM
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A question for the other listers: on the model 1980 with the key on does the fuel pump start and stay on or does it stay on for brief time and then turn off?
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Old 03-21-2024 | 07:57 AM
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I received an email last night from a 1980 928 owner and he says the fuel pump comes on and stays on in the run position .So I think the first order of business is to get a fuel pressure gauge on the rail and see if while cranking you getting fuel pressure.
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Old 03-21-2024 | 08:24 AM
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let the car cool down last night and tried to start. no go. This morning went back to the car and tried to start thinking if it was a connectivity problem or ground the moisture from the morning air might make a difference. It fired but would not keep running. much like a fuel problem. Found some relays so when I get time and it warms up with try the fuel pump relay. get it towed home where I can trouble shoot it if that doesn't work. will keep you posted. david
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Old 03-21-2024 | 09:31 AM
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If an 80 is like the CIS K-Jet in my 79, the fuel pump should prime for a few seconds then stop. My 81 Euro S had a hot start issue that was related to the temp sensor and cold start injector where it would get too much fuel like the cold start injector was firing even when hot. I worked a new temp sensor but that didn't fix it. What I ended up doing was wiring a cutoff switch to the cold start injector. When the car was cold, the switch kept things connected as normal but when it was hit, I'd push the button on the switch to disconnect power from the injector and it would fire much quicker. Would still take a few seconds to clear it's throat once running but after that would run perfectly.

Do a test where after driving the car you disconnect the electrical plug from the cold start injector and try to start the car. If it starts, you may have the same issue I did.

Also you don't want to pump the accelerator when starting it, you want to hold it fully open to clear the fuel vapor from the lines as new liquid fuel pushes it out.
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Old 03-21-2024 | 10:23 AM
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First thing to do is figure out if you have not enough or too much fuel./
So go ahead and Follow Pete's suggestion for troubleshooting.

What is going on with the system is that once the engine is hot then fuel must be kept under high pressure so it wont turn to vapor ,
and thus the injectors being close to the hottest parts turn liquid into vapor if the pressure drops to below the pressure of hot fuel.

Now there are few different ways for the CIS system to loose pressure,

NOTE The fuel distributor and WUR are also suspect parts ,
but for the sake of this discussion ,
since the engine appears to be running pretty well from cold.

The most common in order are,
Too lean of a mixture, cured by turning the mixture screw about 1/16 th CW on the FD, then testing.

the Accumulator, usually the diaphragm starts to leak, it is in the forward of the RR wheel well,

then the fuel pump check valve, this is screwed onto the tip of the pump outlet,

then a dirty injector, this can flood the cylinder to rich, then and cause loss of pressure then too lean because of loss of fuel pressure,
usually cured by replacing the set, the shorter MB injectors seem to work fine,

then the O ring leaking in the pressure feed circuit on the rear side of the the fuel distributor,
remove the needle valve and swap in a new O ring make sure to remove any particles of the old O ring.

The temp sensor on the water bridge the brown one.

NOTE the FP relay has a built in timer it so it should run initially for a second or so then shut off,
if yours keeps running at key on , then the internal diode may have failed.
Test this by replacing the FP relay with a fresh part.

NOTE if all of the easy parts that I listed are known good,
then a deeper dive into the working fuel pressures and running fuel pressures should be carried out.
Though that should have been done if engine performance and running had initially been noticed.
NOTE the parts I listed may all need to be replaced.

NOTE their was a fix for the engine to run from a loss of fuel pressure,
and the was to run a secondary power wire to the cold start valve using a push switch ,
this would activate the cold start injector and it would add enough fuel to get the engine to run the vapors out of the injector lines,
and thus allow the engine to start running.

NOTE be methodical in your testing and notice little nuances write them down for later diagnosis,
also note the fixes that you have applied, so they can be shared here.
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Old 03-21-2024 | 10:28 AM
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The injectors were rebuilt within the last 6 months. I installed them with the new hoses. There's new fuel lines from Greg. Car ran like a bat out of hell after the injectors were rebuilt. Like I mentioned up above the place I would want to start is fuel pressure.

The car starts when cold but does not run so any test on the car running can't happen.

Kevin
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Old 03-21-2024 | 10:41 AM
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Originally Posted by Kevin in Atlanta
The injectors were rebuilt within the last 6 months. I installed them with the new hoses. There's new fuel lines from Greg. Car ran like a bat out of hell after the injectors were rebuilt. Like I mentioned up above the place I would want to start is fuel pressure.

The car starts when cold but does not run so any test on the car running can't happen.

Kevin
If the car starts when cold, but won't run, the first thing I'd do is jumper the fuel pump relay (terminals 30 & 87) to make the pump run constantly.and see if that resolves it. A jumper with a switch and long wires so you can work it from the driver's seat is the ideal scenario. Flip the switch to run the pump when you're ready to start the motor.

If that doesn't make the car run, then you need to get into all the other areas as it means you have a fuel delivery or fuel pressure issue.
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Old 03-21-2024 | 10:51 AM
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Originally Posted by NAVYEOD
car has been a little finicky to start over the last three weeks, only on three occasions. Cold start little slow in catching on today but once started ran fine to work 30 miles. Started as normal when leaving work. stopped at a service station close to home and would not start after stopping. Pumping accelerator no help. Turns over fine. had some one turn the ignition key on while I listened to fuel pump under the car, whines for a couple of seconds then stops (which I think is normal, and eliminates the fuel relay and fuel pump not working). car was running fine and no warning lights. any ideas. About to drive back to my car with some tools and relays/fuses. car has been a daily driver for the last four months and has had high pressure fuel lines replaced and injectors removed and cleaned prior to the last four months. Grounds have been cleaned/ replaced over the last year. No recent work. thanks for any advice..david
Mr.merlins advice is superb as always. Download the Bosch K-jet manual and read it carefully. Your pump runs and stops, great. Since your system has been worked on recently, I would get a fuel pressure gauge and get some numbers. That will help a lot in narrowing down the problem....

Last edited by WestInc; 03-21-2024 at 10:53 AM.
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Old 03-21-2024 | 10:59 AM
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This an US 80 5-speed, which would make this an L-jet car with the M28/13 engine, not CIS (K-jet).
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Old 03-21-2024 | 11:28 AM
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yes L jet
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Old 03-21-2024 | 01:37 PM
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OK I was thinking we were working on CIS,

SO was the green wire replaced? if so did you replace it with a Bosch part?
if not thats the first place to start.

NOTE these early cars take a different fuel pump relay than the later cars,
and simply jumpering them is not the same as having a good FP relay in the socket.

NOTE you also need to have a good fuel injection relay , in essence these relays both work together.
Order both of these relays and replace one at a time and test to see if the engine will run .

Replace the green wire first with a Bosch part the,
URO version has a poorly molded socket that plugs into the distributor and has caused many unstarts
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Old 03-21-2024 | 03:45 PM
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Exactly. I didn't think you could simply jump 30 and 15 on his car. Completely different injection relay.

I really think we need to concentrate on fuel delivery. All this chatter about green wire when there's never been anything wrong with that car maybe just a distraction.
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Old 03-21-2024 | 04:33 PM
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Originally Posted by Kevin in Atlanta
Exactly. I didn't think you could simply jump 30 and 15 on his car. Completely different injection relay.

I really think we need to concentrate on fuel delivery. All this chatter about green wire when there's never been anything wrong with that car maybe just a distraction.
It's 30 (constant hot) & 87 (ground) just for clarity
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Old 03-21-2024 | 04:50 PM
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Kevin on cars with the green wire 95% of running issues are caused by a bad green wire.
So thats where we need to start.

Note if its verified that the green wire has been replaced with a Bosch green wire,
then we move on to fuel.
NOTE you dont jumper the fuel pump relay on these early cars you need a good FP relay and FI relay.

the next step would be to spray some ether into the intake and see if it fires,
if it fires then we look for fuel.


NOTE during the course of my repair history,
I have found 4 brand new URO green wires and they were all bad,
one of them damaged the reluctor ring in the bottom of the distributor, requiring the parts replacement,
in addition to the replacement of the green with a Bosch part

Right now we need the OP to get back with the details of whats been fixed before we do too much guessing

Last edited by Mrmerlin; 03-21-2024 at 09:06 PM.
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