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87 420SEL, starts and only runs a few seconds

18718 Views 41 Replies 9 Participants Last post by  waybomb
87 420SEL, starts and only runs a few seconds - Still need help

Have a 1987 420SEL. 140,000 odometer.

Start the car, rpms come up slow, idles fine, then races and shuts off. If restarted immediately, the process becomes shorter. If a wait of a few minutes, the process may take 45 seconds.

3/4 tank fuel, replaced the fuel filter today, still has same problem. The pumps are running, air filter ok, no wires seem to be off anywhere.

Any ideas on what to check?

Thanks in advance.
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I'm gonna stab at three possibilities-- first and cheapest is the idle control relay, found beneath the false wall in the passenger footwell. I'm pretty sure you'll want to replace that to start with, although it might not be the issue. The fact that is jumps to 2200 when it goes to "closed loop" after a warm-up makes me think it's worth a try though. I'm pretty sure you want P/N 004 545 1032. I have several of these available.

Second is the fuel pump relay, which is found between the two firewalls in the engine bay. I have a few of these lying around-- see which numbers are on yours-- it should be something like 002 545 9205, and it will often have "KPR" or "KVS" on it (not Klima). Pull it and count how many pins it has on it.

The last would be the KE jetronic controller, found on the outer wall of the passenger footwell, behind the carpet. Be careful taking the carpet away-- the plastic it's applied to gets very brittle. I have two of these lying around- #006 545 6032 and #008 545 5232. See if your numbers match.

I'm pretty sure one of us So Cal junkyard divers can get all of these units for you in relatively short order, and pretty inexpensively. As I said, I have a bunch of parts around. If you need something that I don't have, a JY run might be in order. I'm laid up for a couple more weeks after foot surgery, otherwise I'd be out there scrounging, once the water dries up from the recent rains. Mclare (on this forum) might have bits lying around as well-- you can PM him.
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If jumpering the FPR allows the car to run, then that to me means the FPR he used is faulty (the jumper simply bypasses the relay circuitry). Was the FPR he put in a new one or a used one? I'd go for another FPR try.
Hello again... seems this issue isn't going away easily. I'm not suggesting throwing lots of parts at the car, but the three I originally suggested still rank high with me as the potential culprits, with the FPR still looking like the prime suspect. What I'm thinking is that there's a temperature switch that sends a signal to switch to "closed loop" at 50o C or so and the circuitry responding to that signal (call it the "B" path or something) is faulty. It would appear that somehow either the fuel pumps or fuel delivery through the CIS shut down when the car goes to this "B" path, and the engine starves and dies. At one point, you stated that the car runs (and continues to run(?)) when the FPR is jumpered. Without jumpering, starting fluid (and I presume raw gas) would keep it running too, right? I'd suggest you listen for the fuel pumps after the car stalls-- if they are still running (humming), then it seems that the FPR is still doing its thing. If not, then I suggest the Jetronic control is doing something to shut down fuel supply after the "B" path signal. I'm not sure how this would happen, as I'm still a bit of a rookie when it comes to understanding the ins and outs of the CIS controls. Check these links out-- they might be of help...

Bosch Fuel Injection Systems - Bosch K-Jetronic

Auto-Solve Diagnostic Assistance

Untitled Document

Best of luck!!
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Well, now it looks to me like you've got the ICV working right (after cleaning). If it's holding 650-750 when cold, it's looking like the thing works. The next thing I'd look at is the idle speed control relay (the little one in the pax footwell). Strikes me that the box has a bad circuit when the car gets warm and signals "closed loop." The relay then sends an incorrect signal to the ICV which remains open (appears like there's NO signal), and the car races. It could also be that the same signal is telling the FPR to shut down the pumps. So next on my list would be to replace the idle speed controller in the footwell.

I know you have local sources, but I have a few ICV and ICR (speed control) units in my garage, if you need 'em.
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