951North

Car info: 87 944 turbo 95,000mi, all stock except for Lindsay Boost Enhancer and forge BOV.

Driving condition: routine school run, no hard pulling, driving time 10 minutes.

First time this has ever happened, after dropping son at school, was driving ~50 mph and had to brake to 30 for another school zone, after I let off the brake and went back to gas nothing... no revs... just coasted to a stop and heard a pop from exhaust. waited 5 seconds tried to restart, nothing then another pop. Searched on rennlist for similar trouble, read a thread for 10 minutes. Checked IC ines, LBE, BOV, TB boot, all appeared fine. Tried restarting, first crank it fires up. Drive home, kept it out of boost, check cap and rotor, all good (minor carbon buildup, cleaned cap and rotor).

My guess is fuel filter. Any other ideas?

Reason for filter diagnosis is after the car sat for the winter I had a few times where it would not start unless I was jumpstarting it (had to crank for so long it would drain battery, not all at same time but in like 6-10 second tries). After I refueled, it would start fine. Filter has ~30,000 mi.


----------->>>>>>>>>>>FIXED<<<<<<<<<<---------------

It was the transistor on the DME board. Thanks Greg & others!

Paulyy

does it turn off or just die slowly.

NCLA951

When it wouldn't start was tach bouncing?

Tom M'Guinn

The popping in your exhaust is fuel that didn't burn like it's supposed to, which would suggest (but not confirm) your problem is not a lack of fuel. Also, low fuel pressure it likely to make the engine run poorly (like going lean on boost, stumbling, etc.), rather than a motor that either runs just fine or not at all. You'd need to do some testing to know for sure, but in the meantime, next time it happens, watch your gauges closely.

1. The boost gauge should sit near 1 with the key on and the engine not running. If you turn the key on and the boost gauge just sits dead, then you are probably not getting power to the DME/KLR (engine computers). The most common cause for that on these cars is a bad DME Relay. They go bad all the time and are a common cause of intermittent no-start issues on these cars. Worth replacing as a preventative measure anyway if yours is 30 years old...

2. If the boost gauge shows 1 with the key on, but the engine will not fire up after cranking the motor, then look to see if the tach needle bounces/twitches at all while you are cranking. You should see it twitch a little (see youtube videos) while you crank. If not, then chances are the connectors on your speed and/or reference sensors are frayed under the rubber boost and need to be fixed. They also go bad all the time and are also a common cause of intermittent no-start issues on these cars. See many threads here on that.

If it's not one of those things, then pull a plug and check for spark and see if you are getting fuel and go from there. Could be lots of things -- bad ignition (loose rotor, bad coil, bad dme/klr), internally frayed fuel injector connectors (which is all too common), bad ignition switch, bad fuel pump or connection, etc. Intermittent things are more likely electrical rather than mechanical (like vacuum leaks, bad compression, low fuel pressure, etc.) and can be frustrating since they are hard to catch in the act.

gregeast

Another possibility is a cracked solder joint in your DME. I had similar issues a few years ago, the car would just die randomly. Sometimes it would re-start, other times not.

You can reflow the solder in the board, check out my old thread for the details:

DME Repaired w/pics

Hope it helps!

951North

I'll check the dme. Needle bounces. Cap rotor and wires are good and relatively new. When it died it was like the car just turned off

gregeast

At one point before I repaired it, I ended up with the DME on the passenger floor and would give it a whack with my hand when the car died. If you do this at least you'll know it's your DME...

Humboldtgrin

I would suspect the DME/fuel pump relay first. If you have spark and you have injector pulse when this condition occurred I would look into the relay or the fuel pump itself. Also the coil could give you the same sypmtoms. Once the coil cools off it will work for a short time until it gets hot again.

951North

it was the dme

I came out from the grocery store today stared the car and it quit after 15 seconds idle. Would not restart. Had the wife tow me home with my truck, pulled the DME, resoldered the transistor, plugged the DME back in and it fired right up first crank.

Jason.

fejjj

You mean DME relay.

951North

No, the Motronic Box in the passenger footwell, in looking a gregs post it appears he fixed the solder joints on the board, I couldn't get the bottom off the unit to check there... will see how this fix goes.

Before, cruddy flux sweat out of old solder



After new solder

gregeast

Good deal. Now all you have to do is drive around for 6 more weeks on pins and needles before you let yourself believe it's actually fixed, lol.

NCLA951

And that's why I went VEMS!

dlr944

Could the other possibility be the speed and/or reference sensors going bad?

951North

So after I reinstalled the dme it worked for a couple days, then it died again... took out the dme again and soldered on the bottom of the board also. Been a few weeks now and so far so good. The nuts on the dme that are cased in plastic would spin free as the splines had lost their grip. Had to pinch the plastic against the nuts with vice grips to remove the screws holding the bottom board to the dme frame. I haven't taken any long trip yet but I just discovered a new tunnel about an hour away calling my name.