Rufus Sanders

OK, I"ve not posted with an issue for a few years, and was feeling pretty capable, but this one has me stumped.

Upon hard accel. the engine just dies. Sometimes it sputters or bucks and then goes dead as a doornail. However it starts right up immediatly, but doesn't want to do more than a little over idle.

I've changed dist. cap & rotor, plugs, found a vac leak (lower hose to the dist.) that I thought was the cause and after fixing that, it ran fantastic for one day but after sitting for several days first. But driving home from work that day, (about 25 min on highway) it was back to it's old issue.

It almost seems like it'a an igniton timing issue, but the timing seems OK. Plus this issue came on suddenly. I'm wondeirng if it could be a loose timing belt (it is ovedue for one, my bad but it is a non-inter. motor so the risk isn't as high as some...)

Also wonering if it's a bad fuel pump and/or fuel filter (got those ready to put in if so).

Just looking for some ideas or possible similar experiences. Thanks! - Ruf

AirtekHVAC

Well, mine is not a driver yet, but my thought was tank strainer, fuel pump, or filter....I have 2 pumps, and one quit right out of the box, and I could not get any throttle....but idled fine.....not sure if yours has 2 or not...could be....

Rufus Sanders

Thanks Ron, yes I thought that too. Mine has one pump on the outside, so it's easy to change and I've done it before (like 6 yrs ago or more...) so maybe it's due... May dive into that after I hear afew mor opinions - Ruf

Rufus Sanders

Trying to keep this thread alive long enough for some feedback... anyone got some insight? - Ruf

M. Requin

You mentioned distributor cap, rotor, plugs- did you check the condition of the coil HT side? lots of corrosion is frequently encountered there, both the nose of the coil and the end of the HT lead should luck really good, and coil grounds as well.

j.kenzie@sbcglobal.net

Bad air flow meter. Not sure how to check it, but I had mine replaced years ago for a bad flat spot on acceleration, and it fixed the problem. Got a rebuilt. There are threads on afm diagnosis, repair.
Good luck,
Dave

Orantes

I have exactly the same issue. I have owned the car for over ten years so I know it well, but this time I'm leaning towards fuel. I have read multitudes of similar threads on here with these types of issues. Just ordered new fuel regulators and a fuel dampener. Also, ordered fuel filter and fuel check valve. My fuel pump, MAF and Crank Position Sensor were relatively new, so not replacing those.

Mine is a hot start issue. It will start up fine when cold and I can drive for 20 minutes or so, but then the cut-out occurs....then hard to start without pedal pushed flat.

When I replaced the MAF about a year ago, the car just cut out and I was able to limp home. The MAF wasn't an intermittent problem for me though......once it died, it never worked again.

The ignition, fuel pump, brain relays can also go bad and cause cut-out. The ground strap has also been mentioned on here in several threads as a source of intermittent problems. Temp sensor II seems to cause poor running and other issues, but not cut-out in my experience.

Other things...crank end play can cause cut-out or bad brain is always possible. Sometimes the 16 pin connector at the jump post gets corroded and of course, bad grounds are always an issue. The list goes on! I'll be interested to see what you come up with!

Rufus Sanders

Tony,Steve & Martin, Thanks for the insight. I was going to start swaping ut relays tonight so we'll see how that works. The MAF also came to mind and that wuold be almsot too simple, but appriciated...

I"ll give an pdate as I go along. Thanks again for all the help. - Ruf

curtisr

How'd the coil check out as M. Requin suggested?

This might help. It's from Normy who posted this a few years back:

Mine did something very similar for a while; I tracked it to a bad connector at the timing and reference sensor.

This sensor sits on top of the bellhousing and tells the fuel injection computer when a mark on the flywheel goes past. In my case, during acceleration, the ignition would cut out for about 1/2 of a second and then continue as if nothing had happened. If this happened during hard acceleration, it just about launched me through the windshield!

Remove your air filter and airbox via the two 10mm screws. lift upward, and look down in the valley of the V; near the back, there is a square electrical connector secured in a square metal frame. Start your engine and wiggle this wire and see if this causes the engine to cut out. You will want to do this with the MAF installed.

Good luck!

And from rsqrd:

Read the manual. It suggested checking some of the leads to the brain. In fact, the ones related to the throttle position sensor. Pins 2& 5 checked out fine, Pins 3&5 didn't follow spec. So, I am going to check the TPS next. It may be the source of the problem.

j.kenzie@sbcglobal.net

Guys,
This is an 82 US? It does not have a MAF, a TPS or a CPS. It has an AFM. It has plenty of other stuff too. I hope it's a clogged fuel filter, bad green wire or something simple, but I don't think it's an LH-based problem.
Good luck,
Dave

Dave928S

Have you replaced your fuel pump relay and the fuse? Fuel pump fuses often become resistive at the contact points and overheat ... and as a consequence don't give full voltage at the pump. Also check grounds, which give the same outcome if they become resistive as a result of corrosion.

The Forgotten On

Do the usual and replace all aluminum fuses with copper and brass fuses you can get from Mercedes and replace all Fuel dampeners and pressure regulators on the engine and it wont hurt to replace the cold start injector WYAIT. If your green wire doesn't look bright green, replace it and if your fuel pump is making a lot of noise replace it. I will list some of the parts I could find that are the lowest price.
you need one of these: 2 of these Good luck, I replace these parts on my 1981 US (same engine and ignition as yours) and it helped give it a lot of more power and no flat spots aside from S*** running for the first few minutes when the engine is cold. The only parts on that list I have not replaced is the green wire and the fuel pump.
Good luck

namasgt

Try this:
https://rennlist.com/forums/928-foru...cylinders.html

Mine is a S4 but wont hurt to check the injector wires on your 82 S. The wire was broken on mine. It would run fine when the wires were touching each other but when they separated or almost separated the car would run like crap (low rpm) or shut down.

Rufus Sanders

OK, here's an update:

I replaced the fuel pump and filter with new ones, made no difference.

I looked around under the car for exposed wires, broken insulation etc, did find a few questionable things and took care of thoe: No difference.

I pulled the AFM and checked voltages at fully closed and fully open and got the proper readings on the signal and air temperature pins.

Checked my Green Wire and it looks good and jiggled it at idle and it still idled fine.

Bypassed the ignition and Fuel pump relays and car still showed same issue.

I'm now thinking that it is the L-Jet EFI brain, or the crank position sensor, but I msut admit, I've not checked the crank pos sensor it on my '82. So.... I'll get on that and get back to yall later.

Thaks for all the insight. - Ruf

Rufus Sanders

OK, all Shark Humor aside... I'm realizing that Ii did not check the AFM for unusual voltage all along it's range. I'll do that but I'm still left with the L-Jet brain as the cause. Also, I made a terminology error, I jupered the EFI rleay , not the "ignition relay" . Lazy terminology... one else with an old L-Jet shark have some insight? More later - Ruf