[T3] Diagnosis help for a badly running 1971 VW 411

Jens Vagelpohl jens at type4.org
Fri Aug 30 10:57:37 PDT 2019

> On 30. Aug 2019, at 7:28 , Jim Adney <jadney at VWType3.org> wrote:
> Any good news on the Minnesota Type 4 that you're trying to resurrect and 
> buy?
> Any chance it could be a resistive relay, like William may have just found?

Hi Jim,

That story is ongoing…

I had told the owner I was going to get an MPS, but he actually got a used one himself as well. Seemed a perfect match, numbers are the same, down to the yellow mark mentioned in the parts book. He got his first, put it in, and it seemed to make a big difference. The car ran a whole lot better, the backfiring into the intake was gone, and power seemed adequate. He had it up to 75 mph. That was last week on Thursday.

He did another test drive last weekend and it started the backfiring again. Power output was down as well. The symptoms are not identical, but similar to the initial state. He tried all three MPS units he has on hand, and also installed the trigger points you sent to him. None of it helped. His immediate thoughts were the injectors being clogged, or not getting good signal, e.g. due to a bad ground somewhere.

I don’t think it’s a fuel delivery issue. That doesn’t jive with the initial improvements after switching the MPS. I was thinking more along the lines of “what is it that you move/wiggle/influence when you switch out the MPS”, like maybe a cabling or plug issue.

He apparently found someone knowledgeable about 30 minutes away and will take the car there.


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