78 Beetle Starts, then Stalls

[email protected] · Post by **[email protected]** » Thu May 16, 2002 9:20 pm

My 78 Super was running fine--then....while sitting still idling for a few minutes in the parking lot it stalled out. Now it restarts but stalls immediately after it starts up. She's still fuel injected....wonder if anybody has any ideas where I should begin! I'm pretty much a novice mechanic.

superdrag73 · Post by **superdrag73** » Thu May 16, 2002 11:17 pm

Check the fuel filters, and the lines for clogs or plugged filters.

ray greenwood · Post by **ray greenwood** » Fri May 17, 2002 7:28 am

A little bit of spock type logic will help. So...as it warms up...it won't idle. It sounds like basic fuel mixture adjustment is off. I say this becasue in 4-8 minutes, the time period it takes to close the Aux. air regulator, you are losing either the fuel or air you need to keep idleing. Why has the mixture changed in the first place? Be sure it has first. If the Aux air valve is not closing, as the car warms up, and the CHT changes your fuel mixture, an Aux air reg NOT closing could cause this problem by itself. Things that are also suspect are the CHT itself. They get weak with age and send resistance signals that are not in sync. with what the engine may need at its current heat level. Also a very filthy air cleaner can cause the car to run so rich that it cannot adjust. As the previous post stated...a dirty fuel filter can also reduce fuel pressure enough to change the mixture. A fuel pressure regulator weak with age will also start you with reduced mixture and leave you lean once the thing is warmed up. Change your filters first. Put a guage on the fuel loop next. Since the fuel pressure regulator is inside the engine compartment, it gets warm. As these parts age, and the diaphram spring gets weak...they can bleed too much pressure past the loop when they get warm. Look for a pressure drop when warmed up. A vacume leak is also suspect. Leaks at the throttle body gasket, injectors and boots can cause this same problem as the air that gets past them is not metered by the AFC...so no fuel is added. If all else checks out..disconnect the 02 sensor if you have one. If the problem goes away...but the car is now just a bit sluggish...that may be the culprit. Check it with an ohmeter. Ray

susansms · Post by **susansms** » Fri May 17, 2002 7:52 am

Not sure I was clear in my original post. It doesn't stay running for 4-8 minutes now--it stalls immediately--doesn't even idle for a minute.

rich2481 · Post by **rich2481** » Fri May 17, 2002 12:15 pm

check point gap and obvious stuff, Brittle hoses and such. the rest gets kinda complicated.

ray greenwood · Post by **ray greenwood** » Fri May 17, 2002 7:09 pm

Dang...you are right...I missed that in your post. I would bet that superdrag is correct. Pile of crud in the tank does this...or point gap slippage. Hello papa G!...no it was nothing good...just a series of 7 day work weeks. Business is good...but as a salaried employee...I am now making less wages than a stint at dairy queen...at 110 hours a week. There are not even engines incolved! Ray

PapaG · Post by **PapaG** » Fri May 17, 2002 11:46 pm

Hey Ray>
Nice to see you back... I hadn't seen you post for awhile... Hope it was som'n good.

Bruce2 · Post by **Bruce2** » Sat May 18, 2002 7:47 pm

I know this one because it happend to me. You can start it easily and it will run for 3-5 sec and stall. Re-start it a hundred times and it stalls after 3-5 sec.
Here's how the system works:
The fuel pump gets 12V from the crank position of the ignition switch. This creates the pressure in the fuel lines so the car will run. When the engine starts, you let go of the key, removing the 12V from the fuel pump. This is where the airflow meter comes into play. There are a set of contacts in there so that when the engine is running,(airflap open) the airflow meter tells the double relay to continue to supply the fuel pump with 12V. This is not happening in your car. To verify this, you could crawl under the car and remove the small wire from the starter. Then turn the ignition switch to the crank position. Since the starter is disconnected, you will be able to hear the fuel pump. It will give a good healthy buzz, indicating that the pump is good. Now open the aircleaner and remove the airfilter. With the key on, feed a stick or long screwdriver into the airflow meter to open the flap. The pump should run if the key is in the on position. I bet the pump won't when the airflow meter is triggered indicating where the trouble is. I don't have the wiring diagram, but I think the two terminals on the right side of the connector are the switch. Someone??? In my case the airflow meter was fine, the wiring harness leading from the airflow meter to the ECM had chaffed through breaking the circuit. On mine it happened right where the harness passed over the top of the fan shroud.
Good luck and let us know the outcome.

Richard Hunt · Post by **Richard Hunt** » Sun Jun 02, 2002 8:23 pm

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by [email protected]:
My 78 Super was running fine--then....while sitting still idling for a few minutes in the parking lot it stalled out. Now it restarts but stalls immediately after it starts up. She's still fuel injected....wonder if anybody has any ideas where I should begin! I'm pretty much a novice mechanic.<HR></BLOCKQUOTE>You didn't mention if you can still keep the engine running although it doesn't idle, if so you may want to check for intake leaks at all of the hoses and vaccum lines on the motor, also check the throttle body boot for cracks, but you must remove the boot and inspect it for cracks all around. The other info you got from these other guy's is excellent, good luck with your fix.

Rick (M.C. Drag Racer)

Post by **Marc** » Fri Jun 07, 2002 2:04 pm

Prime cause of this symptom is induction leaks like Richard said - if you're lucky it's just one of the smaller hoses which plug in to the intake air elbow and will be a cheap & easy fix. If the elbow itself is bad, you can actually drive the thing with a screwdriver shoved down its throat like Bruce2 mentioned - the mixture won't be right but you can limp it a short distance.
The double relay (behind the back seat next to the ECU) is a fairly high failure rate item too. If you pry the cover off of it and hold the contacts closed you can keep the pump running too (takes an assistant riding in the back seat or some stout rubber bands).
Neither technique is a repair of course, just some handy things to know in an emergency that could save you a tow bill.
Once you find the problem I have a complete `77 FI system for parts (except for a bad relay). [email protected]
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"For every complex problem, there is a solution that is simple, neat, and wrong." --H.L. Mencken
`67, 69, `77 Beetles, `73 II (Type I engine), `86 Audi 5000s, etc. etc.
Independent VW specialist shop manager/unit repairman 1978-1991
Lots of good links in my Yahoo! Briefcase http://briefcase.yahoo.com/marcvellat

[This message has been edited by Marc (edited 06-07-2002).]