1981 Vanagon backfire through intake

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energyturtle
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Re: 1981 Vanagon backfire through intake

Post by energyturtle » Sun Jul 03, 2016 11:46 am

Latest post of the previous page:

Yes mechanical advance works as well. I have changed my distributor out with 2 known to be good ones. The results were the same.

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Re: 1981 Vanagon backfire through intake

Post by energyturtle » Sun Jul 03, 2016 12:42 pm

Y'all ready? It was a busted fuel line. The culprit was the line that comes out of the fuel pump to the engine. It was busted on top, the bottom looked perfect. It had sprayed enough fuel to strip the undercoating of the bottom of the bus. The first one of you who sees me, slap me in the face for "assuming". .....ughhhhhhh.
Scottie

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Re: 1981 Vanagon backfire through intake

Post by energyturtle » Sun Jul 03, 2016 1:59 pm

I found a busted fuel line coming out of the fuel pump where it feeds the engine. I thought that was my culprit. No go. Now it will start, and idle but no rev up under throttle? Fuel pressure is good. I replaced all vacuum lines and tees. The vacuum system is sealed. What am I missing here?
Scottie

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Re: 1981 Vanagon backfire through intake

Post by energyturtle » Sun Jul 03, 2016 2:10 pm

I just pulled the plugs again. Carbon, sooty, fouled mess. I just cleaned them again, before I started it this time. It fouled the plugs in a minute or two of running. What could cause this rich condition so quickly? I'm losing my patience, and fast!
Scottie

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Re: 1981 Vanagon backfire through intake

Post by asiab3 » Sun Jul 03, 2016 4:05 pm

A bad or disconnected TSII could cause that level of richness, or an unplugged AFM. Or excess fuel pressure. All of which need empirical testing.

Robbie
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100k miles with me.
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Re: 1981 Vanagon backfire through intake

Post by SlowLane » Sun Jul 03, 2016 4:23 pm

Does the fuel pressure track the manifold vacuum?
'81 Canadian Westfalia (2.0L, manual), now Californiated

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Re: 1981 Vanagon backfire through intake

Post by energyturtle » Sun Jul 03, 2016 4:31 pm

Ok. Here is the end of day report. All vacuum lines fixed, including intake runners. Ignition system is in good working order. Valves are adjusted properly. Compression test yielded 145-150 PSI on all cylinders. Fuel pump will pump a litre in 30 seconds. All fuel lines and filter checked and or replaced. AFM swapped out with a known to be good one, results are the same. All grounds checked, and cleaned for contact. On my final attempt this evening, I cleaned the plugs again, reinstalled, attempted to start. It would start briefly (2-3 seconds then die). I attempted start up 3 times with the same results. I removed the freshly cleaned plugs. Cylinders 2,3,4 are covered with soot and dry. Cylinder #1 is clean, but wet. WTF is going on here. I hate to say it, but ECU?
Scottie

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Re: 1981 Vanagon backfire through intake

Post by energyturtle » Sun Jul 03, 2016 4:34 pm

SlowLane wrote:Does the fuel pressure track the manifold vacuum?
I'm not understanding what your asking? I do not have a fuel pressure gauge, or vacuum gauge available. I could only check the fuel pump output, and take the FI off, disassemble, and replace all visually faulty vacuum lines, tees, and intake runners.

Scottie

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Re: 1981 Vanagon backfire through intake

Post by asiab3 » Sun Jul 03, 2016 7:13 pm

energyturtle wrote:
SlowLane wrote:Does the fuel pressure track the manifold vacuum?
I'm not understanding what your asking? I do not have a fuel pressure gauge, or vacuum gauge available. I could only check the fuel pump output, and take the FI off, disassemble, and replace all visually faulty vacuum lines, tees, and intake runners.

Scottie

This is your next plan of action. The pump can put out 60+ PSI of fuel through the stock system, and volume and pressure are separate yet related. We need to know if your fuel pressure regulator is properly regulating fuel pressure. The manifold vacuum is what signals the FPR to raise or lower pressure depending on demand. Lots of throttle = low vaccum = more fuel. Little throttle = high vacuum = less fuel.

You will definitely want a fuel pressure gauge that reads up to 60 or 80 psi for work with any L-Jet diagnosis. In fact, we should have done this a page and a half ago on this thread…… FPRs go bad from sitting more than they go bad from operating, so if this van sat for a while, it is suspect for multiple reasons.

Robbie
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100k miles with me.
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Re: 1981 Vanagon backfire through intake

Post by Amskeptic » Mon Jul 04, 2016 6:09 am

energyturtle wrote:Ok. Here is the end of day report. All vacuum lines fixed, including intake runners. Ignition system is in good working order. Valves are adjusted properly. Compression test yielded 145-150 PSI on all cylinders. Fuel pump will pump a litre in 30 seconds. All fuel lines and filter checked and or replaced. AFM swapped out with a known to be good one, results are the same. All grounds checked, and cleaned for contact. On my final attempt this evening, I cleaned the plugs again, reinstalled, attempted to start. It would start briefly (2-3 seconds then die). I attempted start up 3 times with the same results. I removed the freshly cleaned plugs. Cylinders 2,3,4 are covered with soot and dry. Cylinder #1 is clean, but wet. WTF is going on here. I hate to say it, but ECU?
Scottie

I just did a Vanagon no-start in Mankato MN that had stumped the owner and the experts for several months.
It was a weird one. It would start and run for a second then die. Eventually found that the ECU injector signal ground (#5) was grounded at the oil pressure switch. It would run only until the engine built up oil pressure!

You need to follow a specific diagnostic track to keep your exploding variables under control.

Runs? At all?
Ignition is very likely to be OK.

Runs - then dies? Sounds like fuel pump shutting off between starter activation and AFM 36/39 contacts closing to keep the fuel pump running.
Check by turning on the ignition and moving the wiper with the ignition on. Does fuel pump run? Now confirm by putting test lamp on fuel pump terminals and energizing the starter. IF the light stays on DURING the brief engine run, the AFM has done its job.

If above is OK, the other weird possibility is injectors losing their ground path. There are three known grounds, #16, #17, and #5 off the ECU that ground at the crankcase under left side intake runners. Bentley says that there is another one sprouting out of the harness closer to the alternator. The one I saw was closer to the distributor.
Grounds, ya won't leave home with out them.

How much fuel is the tank? How frisky is the battery? Since the injection needs 10.7V during start, and the starter pulls the voltage down pretty good, you need a fresh charge on the battery.
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 91 414 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,113 miles

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Re: 1981 Vanagon backfire through intake

Post by SlowLane » Mon Jul 04, 2016 7:17 am

energyturtle wrote:
SlowLane wrote:Does the fuel pressure track the manifold vacuum?
I'm not understanding what your asking? I do not have a fuel pressure gauge, or vacuum gauge available. I could only check the fuel pump output, and take the FI off, disassemble, and replace all visually faulty vacuum lines, tees, and intake runners.
Sorry, I was making assumptions about your level of familiarity with the system.

What Robbie said. The fuel pressure should be at about 36 psi with no vacuum on the FPR, and about 30 psi with idle vacuum. Those values don't have to be spot on. The important thing is that the fuel pressure tracks the manifold vacuum so that the effective pressure seen across the injector input and output remains constant. That's how L-jet manages without a MAP sensor for the ECU. With constant pressure across the injectors the amount of fuel squirted is directly proportional to injector firing duration under all manifold pressure conditions. The ECU then doesn't need to worry about compensating for manifold pressure.

Also, have you performed the electrical resistance checks at the ECU plug as prescribed by Bentley?
'81 Canadian Westfalia (2.0L, manual), now Californiated

"Wisdom comes from experience. Experience is often a result of lack of wisdom."
- Terry Pratchett

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Re: 1981 Vanagon backfire through intake

Post by energyturtle » Sun Aug 07, 2016 7:27 pm

Fast forward to now. I pulled the FI off, and threw a progressive on it to verify my problems are not internal. The carb results were the same. Backfiring through the intake manifold, and would not tach up. I hooked a cheapo harbor freight vacuum gauge to it and it's all-over the place. Changed the cap, rotor, and condenser. No more backfires. It still won't tach up. Compression check resulted with 115-125 psi across the board. I noticed the #1 and #3 rockers not moving as much as #2 and #4. This is starting to feel hopeless. .........verdict as of now, flat cam lobe that lifts #1 and #3 exhaust valves. Or possibly, I've gone completely defeated and forgot how to adjust valves.....peaload lifters if I may.

Defeated,
Scottie

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Re: 1981 Vanagon backfire through intake

Post by energyturtle » Mon Aug 08, 2016 6:14 pm

Can anyone post me a pic of a correctly installed distributor drive gear, with #1 at TDC. I think I've found my problem.

Scottie

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Re: 1981 Vanagon backfire through intake

Post by SlowLane » Tue Aug 09, 2016 6:47 am

The Vanagon Bentley has a poor photo on page 13.8, with this description:
- set crankshaft to TDC on cylinder no. 1
- install distributor drive shaft so that offset slot is at an angle of about 12 degrees to the engine centerline (small segment to coil side).

But that's not very visual, so Ratwell to the rescue:
Image
'81 Canadian Westfalia (2.0L, manual), now Californiated

"Wisdom comes from experience. Experience is often a result of lack of wisdom."
- Terry Pratchett

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Re: 1981 Vanagon backfire through intake

Post by energyturtle » Tue Aug 09, 2016 8:19 am

Yep, it was a couple teeth off. My daddy decided to disclose, that he had messed with the distributor gear 4 weeks ago, yesterday. I knew damn well i didn't touch it, so I never verified it. Long story short., I will NEVER ASSUME.

Scottie

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Re: 1981 Vanagon backfire through intake

Post by energyturtle » Tue Aug 09, 2016 3:21 pm

Indexed the distributor driver gear correctly, started it up. It still backfires through the intake on #1 and #3 cylinders. The intake runners s for #1 and #3 get hot quickly. #2 and #4 stay nice and cool as they should. Colin, Robbie, where are you drifting nomads at? I'm almost ready to drop this engine for disassembly.

Scottie

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