Intermittent no-start problem

My car ('86 VW Golf) is seemingly jealous of our other vehicles. Whenever one of them goes into the shop, even for something like an oil change, the car decides not to start. It cranks and cranks, but no start. Once it is in the shop, however, it starts right up and runs fine, until we bring it home again.

The first time it did this, we suspected a fuel pump problem as the noisy thing was finally silent for once. After almost two months in the shop, starting every day or twice a day, we took the car home. A few days later, it refused to start again but we were ready. We checked for spark…yes, we have spark! Listened for the fuel pump. Silence. Jacked the car up to test the wires…and the pump runs again! Started the car up and went home; got the fuel pump (and the pre-pump in the gas tank) replaced two days later (after once whacking on the fuel pump with a tire iron to get it going again).

A week and a half later, the car refuses to start again. Again, cranks over just fine; again we have spark; this time we can hear the fuel pump too, but no start. Again we tow it to the shop; again, it starts right up for them. Day after day.

So…we know it’s turning over, we have spark, the fuel pump runs (so it is at least getting electricity)…what’s left? What else could intermittently go bad on this car and cause it not to start? If we bring it home again, and it malfunctions for us (as it surely will), how can we diagnose it ourselves (we do have a manual and a fairly comprehensive tool kit, at least for working on air-cooled VW’s)? What do we whack on to get it running again so we can take it to the shop sans tow-truck?

sounds like a wiring problem (VWs are famous for that). A wire or connector to the fuel pump could be intermittant. Difficult to find.

Yeah. We tried to check for that, but since the fuel pump was whirring the last time it refused to start, I’m sure it’s getting juice. We assume that whirring also means it is pumping fuel, but we don’t have evidence for that. Not sure how to check that.

i have a question in response to yours. is there some major (or minor) difference in where the shop is and where you park your car? temperature? a hill? river/lake? weird little gremlins that live in the trees? i’m just wondering if it’s some elemental thing that’s at your home and not at the shop that’s affecting it. i wouldn’t know what could possibly cause a problem like that, but it just seemed odd to me that it spent 2 months in the shop and it never happened.

If you can find a mechanic who knows how to check the circuits for voltage drops, amperage draw, ground resistance, and can follow the wires and a wiring diagram, and knows how to do “wiring wriggle tests”, you might fix this problem. Go to this web page at auto zone, and click on Fig 57 and Fig 58. It will show you the wiring for the engine and the fuel pumps.

The car actually refused to start in four different places. I live on an island, so the microclimates (except on the water) are not very different from one place to the other. Once I was on a slope, but the other three times were on level ground, always in the middle of the island, twice on asphalt, which is about as close to the shop conditions as you can get I think. Not sure about gremlins in the trees; I haven’t been looking for them. :stuck_out_tongue:

I’ll check into that; thanks!