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Type 3 Runs horrible
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Laithallos
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PostPosted: Wed Aug 08, 2018 1:30 pm    Post subject: Type 3 Runs horrible Reply with quote

Okay So I have a 69 squareback with the stock D-jetronic Fuel injection system. it took a while to get it running right but when I did it ran beautifully. so about a week ago I was hearing a slight popping out of my exhaust at idle. I decided to do a full ignition overhaul. replaced the plugs with NGK B6HS plugs new wires, new cap new rotor, new point and condenser. still had the popping. and one day while driving it just lost all power couldn't even get out of its own way. letting it idle and pulling the wires one at a time the idle did not change on cylinder 3 and 4. I checked for spark at the plugs nice and strong I did a compression test on all cylinders all 145psi. I redid the valve adjustment all within spec .006 I have pulled the fuel injectors all 4 are not leaking and opening and closing like they should. I checked the oms on the throttle switch and its working properly, I have the early build 69 so its only the two wire throttle switch so it only sees idle has no potentiometer to record off idle position. my fuel pressure is at 28psi. I'm at a loss. oh and I also redid my timing to make sure everything was okay
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raygreenwood
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PostPosted: Wed Aug 08, 2018 10:14 pm    Post subject: Re: Type 3 Runs horrible Reply with quote

For the record....there is no potentiometer in any of the throttle switches. They are off/on switches only. There are also no ohms or resistance to check.

That is one of tbe worst features of the books. Resistance has nothing to do with TVS operation or adjustment. It only tells you if you have poor connections or wirn out,switch paths.

If two injectors on one side are not injecting....which is what it sounds like....its typically a bad ground at the case centerline. Ray
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Intrinsic
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PostPosted: Thu Aug 09, 2018 6:01 am    Post subject: Re: Type 3 Runs horrible Reply with quote

Since the problem seems isolated to cylinders 3 and 4, could this be a bad trigger point contact? They are located in the distributor, in a chamber underneath the breaker points and advance plate.
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Laithallos
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PostPosted: Thu Aug 09, 2018 6:56 am    Post subject: Re: Type 3 Runs horrible Reply with quote

All 4 injectors are working properly, now I've inspected the trigger points before when I had a rich condition. They seemed okay and I know parts fail unexpectedly all the time so know my question is, I didn't see an adjustment for them. So what do I look for besides burn marks and where can I find new replacement trigger points
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KTPhil Premium Member
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PostPosted: Thu Aug 09, 2018 9:08 am    Post subject: Re: Type 3 Runs horrible Reply with quote

Laithallos wrote:
All 4 injectors are working properly, now I've inspected the trigger points before when I had a rich condition. They seemed okay and I know parts fail unexpectedly all the time so know my question is, I didn't see an adjustment for them. So what do I look for besides burn marks and where can I find new replacement trigger points


Are you saying it drives fine now? Or do you still have the problem?

On the early models, the injector ground is not at the center, there are paired ground points on each side near the heads (not sure exactly where, but look for them).

Maybe you bumped off a hose while working on it. This FI system does not tolerate any vacuum leaks. First check the hose from the MPS to the IAD. A loose hose here will also cause the "rich condition" you said you had.

I would suspect the ignition system next. Your problem seemed to start (or get much worse) after you did your ignition service. You say the injectors are working... can you verify spark at each cylinder?

Suspect the FI last... it's almost never the issue. Randomly replacing FI parts gets expensive, and rarely solves anything.
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Mike Fisher
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PostPosted: Thu Aug 09, 2018 10:38 am    Post subject: Re: Type 3 Runs horrible Reply with quote

Unbolt the pairs of injectors & watch them spray fuel on top of the engine to see that they all are spraying similar cones of fuel. $5 Remote Starter Button from Harbor Freight lets you work alone!
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raygreenwood
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PostPosted: Thu Aug 09, 2018 12:23 pm    Post subject: Re: Type 3 Runs horrible Reply with quote

Intrinsic wrote:
Since the problem seems isolated to cylinders 3 and 4, could this be a bad trigger point contact? They are located in the distributor, in a chamber underneath the breaker points and advance plate.


Actually not quite. The trigger points fire diagonal pairs....not side to side pairs. So of 3 and 4 on the same side are not firing....its not the trigger points. If even on cylinder on each side from each paired set is firing....it's not the trigger points.

However its most commonly the grounds from the injectors that cause one whole side to go out. Ray
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rosevillain
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PostPosted: Thu Aug 09, 2018 1:20 pm    Post subject: Re: Type 3 Runs horrible Reply with quote

raygreenwood wrote:
Intrinsic wrote:
Since the problem seems isolated to cylinders 3 and 4, could this be a bad trigger point contact? They are located in the distributor, in a chamber underneath the breaker points and advance plate.


Actually not quite. The trigger points fire diagonal pairs....not side to side pairs. So of 3 and 4 on the same side are not firing....its not the trigger points. If even on cylinder on each side from each paired set is firing....it's not the trigger points.

However its most commonly the grounds from the injectors that cause one whole side to go out. Ray


The early injection systems ground the injectors, in pairs, to an upper cylinder tin mounting screw. One ground per side, with the ECU ground at the case split.
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Laithallos
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PostPosted: Fri Aug 10, 2018 9:32 am    Post subject: Re: Type 3 Runs horrible Reply with quote

I've checked all 4 injectors the grounds are good and I have unbolted them and cranked all 4 are spraying as they should and I've checked spark at all 4 spark plugs at the distributor, then with a screw driver at the plug ends grounded to the case, then finally all four plugs out and the side electrode grounded to the case all 4 are getting spark so I have spark and fuel and air the compression test came back 145psi on all 4 cylinders. This is why I'm at a loss it should be running fine but it's not. Also I checked for vacuum leaks none found. My rich condition was caused by a bad cylinder head temp sensor that's fixed. It was running great for 3 weeks before this happened
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Abscate Premium Member
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PostPosted: Fri Aug 10, 2018 2:19 pm    Post subject: Re: Type 3 Runs horrible Reply with quote

Smoke test that sucker and find the intake manifold leak....
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raygreenwood
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PostPosted: Fri Aug 10, 2018 7:57 pm    Post subject: Re: Type 3 Runs horrible Reply with quote

rosevillain wrote:
raygreenwood wrote:
Intrinsic wrote:
Since the problem seems isolated to cylinders 3 and 4, could this be a bad trigger point contact? They are located in the distributor, in a chamber underneath the breaker points and advance plate.


Actually not quite. The trigger points fire diagonal pairs....not side to side pairs. So of 3 and 4 on the same side are not firing....its not the trigger points. If even on cylinder on each side from each paired set is firing....it's not the trigger points.

However its most commonly the grounds from the injectors that cause one whole side to go out. Ray


The early injection systems ground the injectors, in pairs, to an upper cylinder tin mounting screw. One ground per side, with the ECU ground at the case split.


Yes....as I noted.....it can be a ground causing bo th on one side to not fire....but not the trigger points. Ray
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KTPhil Premium Member
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PostPosted: Fri Aug 10, 2018 8:27 pm    Post subject: Re: Type 3 Runs horrible Reply with quote

Abscate wrote:
Smoke test that sucker and find the intake manifold leak....


X2
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Laithallos
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PostPosted: Mon Aug 20, 2018 10:36 am    Post subject: Re: Type 3 Runs horrible Reply with quote

So. It turned out to be a bad manifold pressure sensor causing all this. can't find one and its over $500 to get it rebuilt so I'm just going to ditch the Fuel injection and go with a carburetor kit
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raygreenwood
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PostPosted: Mon Aug 20, 2018 11:18 am    Post subject: Re: Type 3 Runs horrible Reply with quote

Laithallos wrote:
So. It turned out to be a bad manifold pressure sensor causing all this. can't find one and its over $500 to get it rebuilt so I'm just going to ditch the Fuel injection and go with a carburetor kit


Stop it! Its not that hard.

First...whats "bad" with it?...and did someone tell you its bad...or did you test for it?
If it leaks vacuum....is it either of the two o-rings?...or the diaphragm...if it has one?

And...no...you cannot actually get it rebuilt for $500 and have it be generally usable. It will cost $500...and be so far out of whack adjustment wise that you may never get it running unless you have lots of tuning experience.

Does your 69 have the style of MPS with the big slotted aluminum screw in the back filled with epoxy?...(which is actually the outer full load stop)?

If so you can buy a replacement diaphragm kit...a very well built one...with new o-rings.
http://www.tangerineracing.com/mpsdiaphragm.htm

For $154.00...thats a steal. It even comes with adjusting tools and a new plug for the back that allows work through adjusting of the main armature.

With just a little care...you can remove your diaphragm....and duplicate the center and outer screw settings by counting the number of turns...installing the diaphragm and be done and probably be within 10% of where the original adjustment was ...in about an hour.

If the coils read improper resistance...but are just a little high...that can be fixed...usually....by re-flowing the solder on the wires on the inside....5 minutes. If one or more coils do not read resistance...or if teh guts are rusted...only then is it shot.

You give up too easily. There are only 23 live wires and four main sensors in the system (depending on year)....then the trigger points.
Wink
Ray
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KTPhil Premium Member
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PostPosted: Mon Aug 20, 2018 11:28 am    Post subject: Re: Type 3 Runs horrible Reply with quote

Laithallos wrote:
So. It turned out to be a bad manifold pressure sensor causing all this. can't find one and its over $500 to get it rebuilt so I'm just going to ditch the Fuel injection and go with a carburetor kit


Don't give up so easily! Used MPSs can be found in the classifieds all the time. Just make sure you buy the right part number. Check it for leaks (suck to see if it holds vacuum) and resistance (90Ω between 7 and 15, 350Ω between 8 and 10), and if it passes these two tests, you can make it work well.

https://www.thesamba.com/vw/classifieds/detail.php?id=1011823
https://www.thesamba.com/vw/classifieds/detail.php?id=2187740
https://www.thesamba.com/vw/classifieds/detail.php?id=2008018


'68/'69 use the same MPS, part number 311 906 051 B

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Last edited by KTPhil on Mon Aug 20, 2018 1:50 pm; edited 1 time in total
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Mike Fisher
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PostPosted: Mon Aug 20, 2018 11:47 am    Post subject: Re: Type 3 Runs horrible Reply with quote

Tram adjusts my '69 MPS AFR with a small screwdriver while he has his 02 sensor clipped to my tailpipe. Cool
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