EFI problems-checked search

[Bill Anton]

New to this forum, normaily in the 9112 Registry.

I own a 912E with L-jet. I just had a complete rebuild done by a quite reputable engine guy for P'cars and go-fast VW. For 2 days after I picked it up it SCREAMED! Fast, lots of new torque (especially at 3K +) and really fun. Then the Gods frowned. I must have had too much fun..........It isn't the engine-its the EFI. Starts great for 30 seconds and nose-dives to 300 rpm and quits. Idles rough-really rough. Dies at every stop sign, as soon as I take my foot off the gas. Sluggish on the straights, and gets jerky when at speed if I take my foot off the gas.

Here's the thing that has me wondering. Do to a smoke issue, the wrench had to pull the engine again before I picked it up. He mentioned that my EFI was messed up because he had noticed gas puddles in the intakes. He says to get a new air flow meter.

I have checked the L-Jet manual, and my car meets 4 of the 5 "trouble areas", so I have no idea where to start. All new hoses. All bolts checked and torqued. So where do I start?

Any help appreciated. I know basically bupkis about EFI. Is there someone in the Seattle or Kitsap area that can give me a hand?

Thanks All,

Bill

[Bleyseng]

I am in Seattle and can help some.

Check your CHT sensor first to see why is running so rich. AFM usually don't break unless you backfire on them.

[Bill Anton]

Thanks, Westy.

I would be happy to meet up with you at your convenience. Please give me a call at: 206-780-0342.

[raygreenwood]

Gas puddles in the intakes is caused only by leaking injectors. When the car is warmed up...these would be gone (evaporated) before you could remove the intakes to see it. If its cold and has not been running and you have puddles in the intakes....then that is purely leaking injectors.

Or....if the fuel pressure is too high the injectors may not be resealing.

And if the fuel pressure is too high...you generally have a vacuum leak leaving the regulator in WOT mode .....and/or a rectriction downstream leaving the fuel pressure over its max.

The CHT is a good check......but as the CHT heats up it leans you out.

Generally once the car has been worked on heavily....the most common problems are vacuum leaks. You are allowed "0" vacuum leaks of any kind. Also check all grounds and wires and test the fuel pressure both at idle and with the vacuum hose on then off.
Go to a different mechanic. Ray

[Bill Anton]

Thanks for the tips. I have been over the vacuum system, and it is all new. Everything connected. Ran my hands over every hose and metal piece, and can't find a leak. It does sound as though that might be the issue, but I can find nothing there.

I will be testing the leads on all sensors today to see if something is not tight or is somewhat corroded. Same with the injectors.

How can I actually "test" the pressure regulator, or any other sensors?

Thanks

Bill

[raygreenwood]

Several things. The fuel pressure regulator operates by vacuum. At high vacuum (idle)...you have low pressure, generally around 32 psi. At any major oipening of the throttle...you lose vacuum in the plenum. The pressure rises to a max of about 42-44 psi.

A simple water pressure gauge ($10) and a few feet of hose and a brass barb to connect the gauge to the line is all you need. The gauge for just checking operation of teh regulator (not for serious tuning)...need only be about 0-60 psi in 1 psi encrements. It connects to the fuel ring between # 3 and 4 injectors. There is a little stub sticking out.
While idleing...you should be reather steady at around 32 psi. When you blip the throttle.... it shoudl swing to about 38-42 psi. If at idle it is high pressure....you either have a vacuum leak, a sticking throttle plate (not closing all the way) or a bad regulator.
To further check the regulator... with the car idling.... pull offf the vacuum hose and connect a hand pump (like mighty vac). Pull about 15" hg. If the regulator is good it shop drop to about 32 psi.

If the regulator is good...then you have a vacuum leak somewhere in teh intake system.

Sources of vacuum leaks that will do this are:
Valve cover gaskets
Pushrod tube o-rings
runner to plenum boot connectors
injector seals
intake gaskets
the cork gasket at the oil breather tower
any vacuum hose that is not clamped
a sticy throttle plate.

Also pull the plu from you cold start valve.
also check the cold start valve for leaks. In rare instances it can stick open.

If by chance your fuel pressure is way too high.....you might have a restriction or a crimped pipe downstream of the regulator.Ray

[Bill Anton]

Outstanding information! Thanks much. I will try the tests, but need to wait for someone to start and hold the engine while I am in the back working. It does not hold an idle for more than 20 seconds. Runs prety good over 2000rpm.

[Dave_Darling]

Check the EFI articles over at http://www.type2.com ; the later Buses also used L-jet.

A sudden change like you describe is very likely due to a vacuum leak or an electrical connection of some kind.

Easy check for the AFM: Push on the vane, and make sure it moves smoothly. If not, if it sticks somewhere, it's hosed. They're quite rare, (and specific to the 912E!!) so you might be hosed as well.

--DD

[Piledriver]

I think the last fellow with the same symptoms had a bad pertronix module...

http://shoptalkforums.com/viewtopic.php?t=103137

[Bill Anton]

Found the culprit-it needed a new AFM. Thanks all for your input. I got one from a salvage yard for $150., installed it, and its running like a dream.

Bill

[raygreenwood]

So....what was the issue with the AFM you had? Was it bad resistance in the electronic part....or connections....or as dave mentioned....a flap that is not moving properly? The reason I ask....is that if you found no overt reasons....just swapping parts usually masks what might be just a simple cleaning or adjustment. It is also possible just to have the "pinions" on the flap gummed up.....or have minot tarnish or corrosion on the wiper strips inside of the black box part. I would just hate to see you bypass a part that is in fact still good. Ray

[Bill Anton]

I have yet to determine what the issue was. I plan on testing the AFM this weekend and putting back the original one when I do. I borrowed a working one, and need to return it.