Shuts off while driving - IDEAS?

[Omaha 560SL]

I have a 1988 560SL that has started to shut off while running, but when trying to start it again, it won't fire. If I wait a couple minutes, it will start again immediately. A week ago, I was at a stop light and it just quit as if I shut it off. Turning it over, it wouldn't fire. Put flashers on, opened hood and took off air cleaner cover (thinking it flooded), turned it over and it fired right up. Yesterday, I left home (cold engine), got on the highway (1 mile away) and after about 2 miles of highway driving (65-70 mph), it just shut off as if I turned off the ignition. I put it in neutral and tried to start it, but it wouldn't fire. I coasted down a long hill to an exit and kept coasting to a parking lot. I opened the hood and got out, but without doing anything tried to start it again and it fired right up. Two years ago, I replaced the plugs, plug wires, distributor cap and rotor to resolved a misfire, which worked. I have had the car 4 1/2 years and have put 12,000 miles on it (now at 144k), since it is my summer fun car. Could I have an ingition coil going bad?

[Sugar Bear]

Yes you could. Had an 81 380 SEL doing this and driving several of us crazy until we stumbled upon a heavily corroded; but, rather hidden by its covers, secondary coil wire. Replaced both the coil and the coil wire, problem solved.

Good luck!!!

[freshairfiend]

I once had a 1964 Olds 98 convertible that did exactly what you are describing. Turned out to be a rusty fuel tank that continually clogged the fuel filter

[TX76513]

Your going to have to dig around otherwise anyone is going to be just throwing darts on the board. A very common issue to the problem you have is a vacuum line that is deteriorated. Look for bad lines/connections.

Other things to look at.

Idle Control Valve
Fuel Pump Relay
OVP controls fuel enrichment (Pin #87 should be hot with key on 0 V its bad)
Air Mass Sensor

There are ways to check these components. You don't want to just start throwing dollars at it. Its not the answer you or anyone else wants....we would all like to ask a question and get a reply that its a $2 O ring on ebay and life is good. Dig in there is some very qualified help here that will guide you.

[Omaha 560SL]

Thanks for the suggestions! While I get the problems that could be caused by fuel tank scale that clogs the filter and leaking vacuum hoses, I have to believe the problem is ignition related, since I was driving at 65 mph with the cruise on and it shut off like I turned off the key. I threw it into neutral and tried to restart it, but it wouldn't fire. After coasting to an exit and parking lot, I turned the key again and it fired right up. Any other suggestions?

[Frank Reiner]

Omaha:

As noted by TX above, the fuel pump relay is a prime suspect for the symptom you describe. If it fits in your skill set, remove the relay, pop the cover off, and examine the solder joints for cracks. If a visual inspection does not reveal any obvious cracks, replace the relay without the cover, and resume driving.

[ILUVMILS]

If it were my car I'd unbolt the ignition box and apply some dielectric grease to the mounting surface. It acts as a heat sink so the module will stay cooler. I've done this a few times with success...........

[Omaha 560SL]

To: TX76513, Frank and ILUVMILS - I was able to locate the fuel pump relay and pulled it out, then ordered one after confirming it looked the same, although the part number printed on the current fuel pump relay was very different than the part number shown for a 1988 560SL. Regardless, it arrived today and I put it in this evening, then took it for a drive to confirm it was working. I didn't go on a long ride, but it didn't quit, though I will need to take it out on a longer drive before I know if the problem is solved. If not, then I will add the dielectric grease to the ignition box to see if that does the trick, but I only want to do one at a time to know what the problem was. THANKS!

[Omaha 560SL]

To ILUVMILS - when I read the prior posts about the fuel pump relay, I "Googled" it relating to a 560SL and there were several posts on other sites of the same trouble and a fuel pump relay fixed it. Since it was only a $30 part on PeachParts, I wanted to try this first, then try the dielectric grease if it didn't solve the problem, since the weather was nice the days I had the trouble. However, while PeachParts and every other site I checked shows the part number of a fuel pump relay on a 1988 560SL is listed as "003 545 2505" with a row of 6 pins and a row of 4 pins, the relay I took out has part # "002 545 16 05" with a row of 6 pins and a row of 3 pins. When I "Google" this part #, I found a post on PeachParts that says "It has been superceded by part# A 003 545 01 05". Do you know if the 01 05 has been replaced by the 02 05 that everything says I should have?

[Frank Reiner]

Originally Posted by Omaha 560SL

To ILUVMILS - when I read the prior posts about the fuel pump relay, I "Googled" it relating to a 560SL and there were several posts on other sites of the same trouble and a fuel pump relay fixed it. Since it was only a $30 part on PeachParts, I wanted to try this first, then try the dielectric grease if it didn't solve the problem, since the weather was nice the days I had the trouble. However, while PeachParts and every other site I checked shows the part number of a fuel pump relay on a 1988 560SL is listed as "003 545 2505" with a row of 6 pins and a row of 4 pins, the relay I took out has part # "002 545 16 05" with a row of 6 pins and a row of 3 pins. When I "Google" this part #, I found a post on PeachParts that says "It has been superceded by part# A 003 545 01 05". Do you know if the 01 05 has been replaced by the 02 05 that everything says I should have?

Not to step on another's toes, PN 003 545 25 05 is now the universal replacement. If you look in the relay socket of your car, you should find that position 5, the location of the extra pin of the 25 05 relay, does not contain a sleeve. In vehicles produced after ~01/90 that pin is used for another function. All other pins remain the same.

[Omaha 560SL]

Frank - thank you for the information regarding the replacement part. While it has been running fine, I feel a lot better about swapping out this part knowing it is the correct replacement. I used a small mirror to look into the sockets before I installed the replacement and it appeared there was no metal sleeve in the pin position being added, but still felt a little hesitant about using a different part number than what came out. Thanks!

[Omaha 560SL]

It is now 10 days later and yesterday I drove from Omaha to West Point (NE) for the annual "Last Fling Before Spring" car show (over 700 cars from the region) and had no troubles at all. I think the fuel pump relay was the problem - THANKS!