1980 Vanagon - Troubleshooting a well running engine

Saylrman64 · Post by **Saylrman64** » Tue Mar 06, 2007 2:07 am

Hello all and first I would like to say thank you for letting me join in.

I recently picked up an 80 Vanagon 2L air cooled.
She only ran poorly on 3 cylendars. Since then I have torn down the engine to the block and rebuilt. Everything looked great and all the little things where taken care of. now she runs and sounds great but...

I do not know how much vacume she should be drawing but I only get about 12 to 13 inches at idle.
She idles kind of poorly when she first starts and then pretty solid when warm with less than a 50 rpm fuxuation.

The biggest problem is she has NO top end. I bet I could run up hill faster than her.

I really need to knwo what hte idle vacume should be and any suggestions on the top end would be great.

I have checked the compression and even re-torqued the heads.
She has 135 to 140psi on all four.

Again, she sounds an runs great, just no guts and I thnk the idle should be more stable when cold.

Any help is greatly appreciated, thanks.

Manny

vwlover77 · Post by **vwlover77** » Tue Mar 06, 2007 5:52 am

Stock fuel injection, or carb(s)?

Ignition system all in good condition from the coil to the plugs?

Saylrman64 · Post by **Saylrman64** » Tue Mar 06, 2007 7:54 am

It's fuel injected and everything is stock.
I made a lot of trouble for myself finding replacement muffler, cat, crossover etc.
I replaced with new, the coil, cap, rotor, condeser and points.
I did a lot of air leak chasing in the begining because she wouldn't idle at all. Replaced intake rubber tubes. Found a better intake boot.
Got her to idle but she had this weird fluttery raise to 900rpm then drop down to 650 or so.
Finaly I swapped out the air intake sensor.
Even though the idle was rough i may go back to that sensor just to prove out the top end problem.
As for other things, i have followed the book and proved my injectors, aux air bypass, deceleration valve, fuel pressure regulator, thermo time couple.
Replace air sensor II all together.
Very good EGR and tube etc.

Thanks.

vwlover77 · Post by **vwlover77** » Tue Mar 06, 2007 10:36 am

Have you performed the fuel pressure and fuel volume tests as described in the Bentley manual?

If you fuel pressure is fluctuating due to blockage anywhere or a faulty fuel pump or pressure regulator, that could explain the idle speed moving around.

If the volume of fuel is not what it should be, again due to blockage or a bad fuel pump, it could be causing the poor top end performance.

If you turn on the ignition with the engine off and move the flapper inside the AFM by hand, you can get the fuel pump to turn on. Try this, and see if the fuel pump is excessively noisy or whiny. If so, this is a good indicator of a blockage.

Saylrman64 · Post by **Saylrman64** » Tue Mar 06, 2007 3:04 pm

I have the VW service manual and a Haynes. Both agree on the pressure and volume and yes I did check both.
I propped open the AFM and checked volume at input to pressure regulator. I think they call for 500cc in 30 seconds or somehting like that and I got 550+. I checked at the input to the regulator because then I have verified there is nothing inline all the way there slowing things down either.
As for pressure I hooked up a T and verified whatever was in the book. Something like 28 at idle and 32 on rev.
All checked out.

I do have to do the listen test and now that I have a spare fuel pump I'll swap it out since it is true that even though you get good pressure and flow a few seconds durring testing, it's sustained volume that I have to have.

I really need to find out the intake vacume so I know if I am done chasing little air leaks.
Any chance you have that or can anyone tell me?
Thanks

vwlover77 · Post by **vwlover77** » Tue Mar 06, 2007 6:46 pm

12-13 inches at idle does not sound unreasonable to me - others may want to chime in here. Unless your vacuum leak is major, I don't think a vacuum gauge will help you determine whether you have one.

I looked for vacuum leaks on my engine by plugging the S-boot at the AFM and pressurizing the intake with air from my compressor where the vacuum line to the brakes connects to the air plenum. I then used a spray bottle with soapy water to check all the various vacuum connections for leaks (you can see bubbles).

Have you checked your S-boot (between the AFM and the throttle) carefully for cracks or splits?

I'm running out of ideas!

Saylrman64 · Post by **Saylrman64** » Tue Mar 06, 2007 7:32 pm

If I am in the ball park on the vacume then I know I have no medium size leaks. The big ones keep you from running. I am suspicious of little ones which usually you can determine if you have or do not have simply because your idle screw doesnt do shit no matter how far you turn it.

I chase out leaks the easy way. Get her to idle even poorly, give short pointed shots of ether and when you hit a spot that has a leak, you hear her smooth out real quick.

As for the boot, I did the rubber cork in the little hole while holding my wet hand over one end and sucking on the other end. (hey! it works).
The human air system is pretty atuned to presusre differentials. This is the second boot by the way. The first has a couple weak spots that looked like the where wearing but even it didn't have any leaks.

Someone has to have the exact vacume I would think.

It really seems that the top end problem has to be fuel delivery or air.
Correct me if i'm wrong but If it where poor spark or timing I'd get popping or backfire.

Help! Anyone.

dingo · Post by **dingo** » Wed Mar 07, 2007 9:01 pm

i believe manifold vacuum at idle should ideally be between 18-20.
12-13 sounds quite low to me.

go to this website below...it shows you how to use the vacuum reading to indicate where your problems are. watch the needle while your engine idles and then refer to the chart

www.centuryperformance.com/vacuum.asp

Saylrman64 · Post by **Saylrman64** » Thu Mar 08, 2007 12:18 am

Thanks for your input Dingo.
That site has very good info on guage use but it does have on point of confusion.
In the picture for steady but very low vacume it says "Incorrect Valve Timing" but in the description for that picture it says simply "Late timing".
For a VW, valve timing means splitting the block.

I have never worked on any engine that didn't pull 20 inches so 13 really seems odd.
I know VW' are in class of their own but some thing are universal and I think the vacume range is one of those.
What counts is that if we're right and 20 is a pretty solid min. no matther what you're tuning, I need to find one more leak.

Post by **Sluggo** » Thu Mar 08, 2007 10:00 am

Valve adjustment does not require splitting the case. Remove the valve covers and you are right there.

dingo · Post by **dingo** » Thu Mar 08, 2007 10:13 am

12-13 is a pretty serious leak...OR it could be valve timing OR something else. Keep an open mind while investigating. Maybe ignition timing ? incorrect firing sequence ...i dont know..just throwing things out there. If the needle is steady it means something general, not specific to one bad cylinder.

good luck !

vwlover77 · Post by **vwlover77** » Thu Mar 08, 2007 11:15 am

I seem to remember that 14-18 was normal for these engines...

Can you give more description of what you mean by no top end? Remember that you have a 67hp engine and a 3000+ pound vehicle.....

Saylrman64 · Post by **Saylrman64** » Thu Mar 08, 2007 12:51 pm

That brings up another question!

I get on the freeway and wind up in first then second and tehn third.
If I don't wind out third to 50 or 55 mph I can't shift into fourth.
If I do, I will never get above 50 mph.
God help me if there is an incline involved at all.
In town, under 35 or 40. plenty of take off power and everything.

The little marks on the speedo for shift speeds is scary.
I'm supposed to shift into 4th at like 57mph! She's screemin.
Even the lower two marks seem like i'm windoign her out.

Ugh!

vwlover77 · Post by **vwlover77** » Thu Mar 08, 2007 5:03 pm

I believe the marks on the speedometer are the max speeds, not the normal shift points, so yes, it will seem like you're winding it out!

But during all of this, I do not hear you saying there is any bucking, missing, or backfiring, correct?

Perhaps your distributor is not advancing the timing correctly. Have you checked this with a timing light? With all hoses and wires in place, first check that the idle timing is correct. I believe it is 7.5deg BTDC for your engine just like the earlier models.

Then, watch the timing as you gradually advance the RPM to somewhere to near 3500 RPM or more. The timing should advance (move left) to nearly 40 deg BTDC, maybe even a little more.

If your distributor is not advancing properly, the engine will not make power.

Saylrman64 · Post by **Saylrman64** » Thu Mar 08, 2007 5:22 pm

1) To be certain, the single, double and triple red dots on the speedo are the max shift points?

2) This motor sounds great the whole time. No popping, backfires.
Just no power. I do still have the isse that when she is cold and I first start her she idles quite low for the first 5 minutes. I think that is part of the low vacume I am chasing.
(Still can't get a solid [from the book] vacume number to know if I have a leak or not.)

3) I have of course checked the vacume advance but not beyond maybe 15 degrees you see when you give a rev after setting it.

Itinerant Air-Cooled

Itinerant Air-Cooled

1980 Vanagon - Troubleshooting a well running engine

1980 Vanagon - Troubleshooting a well running engine