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V8 Question ?

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In my 90 I have a RRC 3.5 V8 4 sp auto - flapper. Had trouble starting recently -so new battery, disconnected 9th injector all hunky-dory. Tried yesterday, engine just whizzed over, almost fired, then just whizzed over. No problem, went to work on the pushbike. Thought it might be damp dizzy, coil, fuel filter blocked, fuses etc etc. Cleaned dizzy cap, WD40 etc, still no luck, checked the fuses, I did find a 20 amp blown, didn't have one, so popped in a 35. Before I tried to start I also popped the relays out and swapped them over, voila fired up first turn. Went out to get some 20 amps, put one in place of the 35, wouldn't start again, messed about with the relays, it started. So I'm thinking duff relay, so I need to get one or two of those. When it started I took it for a run, and while it accelerated ok and shifted through the gears it didn't feel "right". Can't put my finger on it, so when I came back I popped the bonnet, revved it up a bit, and I don't know,just didn't seem ok :blink: Sorry if its a bit vague. I did notice the small vacuum pipe out the back of the plenum which splits in two, looks a bit perished and cracked. While the engine was running I pulled this pipe off and the motor seemed to run a lot sweeter and rev a lot more freely. Can anyone tell me what this pipe does for the motor, and if I re-new it will the running/performance improve. Sorry to be vague,but just looking for something that might be a problem. At some point in the future I'm pretty sure I'll megajolt, or maybe megasquirt which should get rid of all the starting and running issues.

Thanks in advance, Jon

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The Vacuum pipe feeds both the fuel regulator and the overrun cutoff switch.

Both of these items have their issues …………. The fuel regulators get lazy and deliver at low pressure ………… the overrun cut off switch often goes open circuit, however, this fault would lead to an engine shutdown or total non start as it cuts the feed to the overrun cutoff relay which in turn removes the engine running signal from pin 1 of the ecu. You can bypass this switch by just disconnecting the two switch wires and then joining them together, however, as they are always live they must be insulated.

I would be inclined to renew the vacuum pipes and see if that improves matters.

If the original relays are the bosch type in the sealed metal cans …………. These rarely fail.



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Thanks for both replies. BBC - Yes they are both Bosch metal relays, the one appears to have some slight "white" fur corrosion on the pins, but not a lot. I think I'll start by renewing the small vacuum pipes as a matter of course and see what happens. Can you get this pipe as a kit or similar ? Would plastic pipe be better, such as water washer tubing, or would this be too rigid ? Thanks again, Jon

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