85 Jetta GL - Shutting off while driving

[rviebrock]

I have a 85 Jetta GL gas (unmodified) with 352k on it.

Strange thing happened to me last week on the way to work (weather was clear / sunny). Travelling at 120km/h the tach dropped to 0 and it was if the engine stalled, the oil and bat. lights flashed (radio still was on). i pulled over to the shoulder and parked, shut the car off and tried to start, would not turn over. Had to wait 5 min or so before it would start.

Then 2 days ago, same thing happened but no lights flashing on the dash, just as if you had no keys in the car, tach to 0 and coasting to the side of the road (also around 100km/h).

Yesterday on way to work 120km/h same thing happened (no lights) but 5 sec. after the tach dropped to 0, it fired up again, had a bit of a back fire since I was still moving at 120km/h and carried on to work.

Now all three times I have been going to work in the morning and there was no rain or moisture (maybe a bit of fog / morning dew). I do park the car in the garage everynight because if it gets damp, it wont turn over or is very hesitant in want to accelerate.

Recently had all the distributor / wire / ignition coil / ignition switch changed.

Does any one know what is wrong with my baby?

I have heard possible fuel pump relay? Something grounding out?

The roads are relatively smooth (no potholes). There is also no warning when it is going to happen.

Also to help diagnose, when I turn the key to the first setting (ACC.) there is a hum for 2 or 3 sec. from the back of the car under the fuel tank filler ( I assume this is the fuel pump kicking in for a sec or two / or is this the hum of something not working?)

Please help.

[stevethefolkie]

Couple things to check -

first off - your engine, battery and chassis ground points (can't recall if the alternator had it's own ground) - they should all be nice and clean and snug. Paint, grease, spooge and filth don't make good ground points, and neither does rust - bad grounds have caused countless problems.

Then I'd take a look at the (rather fragile) HAL sensor and wiring - it's the small diameter wires coming out of the distributor housing from a small plastic connector (below the distributor cap) - it's really easy to screw one of these up while changing the cap or setting the timing - I broke one when I dropped a wrench on my dear, departed GLI.

I'd check the battery, under load (your local autoparts store should do that for you for free) - occasionally you can have a cell crap out in the battery which will make it weak. Lights and all will work but it won't have the amps to crank over the car - and on occasion they can heat up and short internally - killing all power to the car.

Failing the above (they all check out OK) I'd swap in a known, good ECU and see if that clears it up.

The hum from the tank is normal (it'll engage for a bit on startup then, if there's no signal from the ignition indicating that the engine is running, will shut off - this is a safety feature to ensure than in the event of an accident the fuel pump doesn't keep sending pressurized fuel through a potentially broken fuel line) - but as to the fuel system - when was the last time your fuel filter was changed? They can accumulate junk over time and clog -


Best of luck

Steve

[rviebrock]

I'm back.....

Well here's what has happened since original post.

After a tow or two and some cursing, the jetta wouldn't turn over. Hit the starter solenoid with a hammer, fired up, took it to the mechanic.

Battery was replaced (7 yrs old), new terminals on the wires to the battery, cleaned the contacts, new starter and solenoid installed.

Car works great until last week. Driving home car shuts off while doing 100 km/h. Engine / Oil red lights only come on when I put the car in neutral and take foot off of clutch. If i left it in gear lights do not come on since car is still turning alternator / engine. Takes 10 min on side of road to restart. Cranks fine would not turn over.

Happens again following week. two days later happens again but backfires and refires 3 sec. after it shuts off, I didn't have time to do anything, then shuts off 15 sec. later, pull off to side of road and stop. Restarts after second attempt. Cranks fine, just didn't want to start.

I have no mechanical background but have talked to my 'guy' at shop, experts on VWs, owns the same model I have.

Mentions a few things, could use imput from you experts.

Fuel pump relay (heard they get a vacuuum some times and was actually recalled in mid 80s for design flaw, new mesh filter added to prevent it0

ignition wire from fuse box to coil may be corroded

engine speed sensor wears outs, resistance builds up, ECU thinks its an open circuit the shuts off and wont start till cooler.

secondary fuel pump (can't remember what he called it) if its not getting pressure gas doesn't flow engine shuts off. He said it is more likely when gas level is low, which if i remember it has been when this happens. 1/4 tank yesterday when the multiple times occured.

I don't think it is electrical because all lights work when it shuts off, and to have to wait 10min on side of road before it starts again seems like fuel or overheating issues. Has happened at speeds between 70 and 120 km/h with out warning. Has backfired started seconds afterwards, or have had to wait 10 min on shoulder. Engine has always sounded like it wants to start just not getting that last umph! Turn key to ON and the humming from the back for 3 sec. sounds normal.

HELP!!! Just need ideas mechanic can check. Fuel relay sounds like a good idea or going to swap ECU with a used one. Cheap ideas are better to start with.

[92cabby]

our 92 cabby is doing the same thing. When we get less than a quarter tank the car stalls and will just go dead while driving. also has annoying humming sound at rear of car when fuel gets low. Any Idea ????

[BadBradokc]

I have a '85 Jetta GLI, that had the same stalling problem. I thought that the fuel filter was clogging up but changed about 5 months ago. Put on a new fuel filter did same damn thing, would randomly stall, then start back up and run fine. The problem is the transfer pump mesh screen that snaps onto the bottom of the pump. There is a 3 screw cover in the trunk you call pull the pump out and clean the screen. I cleaned mine and hasn't done it since. It even starts ALOT faster.