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For a while I've been puzzling with the slow cranking problem with my '89.
I discovered that if I stop cranking and QUICKLY start cranking again it often roars right to life.
I thought this was only from a bad fuel system pressure check valve, letting fuel pressure drop right after shutoff and the fuel pump not getting enough current while cranking to re-build pressure easily. I figured the pump was getting a brief shot of strong juice in the tiny bit of spinning the cranked engine still was doing as I turned the key back past RUN to off. And therefore, fuel pressure was primed and engine ready to fire on the re-crank a second later.
So I put in a push-button switch to trigger the fuel pump manually, and have been doing this for a few seconds before turning the key. It helps SOME, cutting cranking from say 7 embarrassing long turnovers of engine to 3 turnovers. But it's still not right and it's definitely not the entire answer, doesn't get me that instant roar to life we all deserve from our cars. (And that they are all capable of, even in high miles and late life.)
Then the other day I discovered: pop the clutch to start the car on a hill and it starts almost immediately, the way I would expect a nice smooth-running car like the 900 to do. This is even without pre-pressurizing the fuel system by the way.
So it seems to me that the current drain while cranking the starter is pulling juice away from either the ECU or the coil and that that is the real reason for the long cranking.
Anyone have any experience on this point? Could the drain be in the ignition switch? Has anyone who replaced this switch with a new one experienced a cure to long-crank starts, for example?
Or might running a heavier gauge wire to the coil help things out?
Electrical pros, step up to the plate please!
(By the way, to pre-run your fuel pump, on all LH cars, look for the tiny "violet" wire to the fuel pump relay on the passenger wheelwell behind the carpet, that runs from the ECU to the relay. Tap into this with one of those clip-on connectors (I used one that accepts a 1/4" spade lug) and then when you ground that wire with the ignition switched on, the fuel pump is triggered. That wire can be found in the large bundle of wires that leads to the ECU plug, you don't need to reach way up and tap it near the relay itself. It's unique, smallest gauge and light purple color, easy even for color-blind me to find. Tapping it is useful also if you ever want to run your fuel pump for other reasons including to test it.)
First thing I'm gonna do is go to a nice long hill and do lots of experimenting with jump starts.
Second thing is, pull out my Bentley and Haines and start reading the wiring diagrams and looking under the hood.
posted by 70.105.237...
, Sat, 24 May 2008 21:33:54
, Sun, 25 May 2008 08:29:53
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