After putting some fuel in, the car wouldn't start. Closer investigation suggested that the fuel pump wasn't running - the cheapest and most likely candidate here was the relays, so after lots of faffing about with a multimeter, I got a couple of new relays off Ebay for £10 and tried again, with the same result. The relays seemed OK, so I took the fuel pump out and had a look. One of the terminals on the pump was burned, suggesting it had been damaged in the past, so I hit up Ebay again for a new pump... which didn't solve the problem.
The pump gets voltage for two seconds as soon as the key turns, to prime it, but then nothing more (at least this shows the pump wiring is good). Similarly, there's no spark, so, it seems that the ECU is unwilling to start the engine. Likely candidates are the crank position sensor (aka CPS) and the cam position sensor, so I replaced both of these (the former was a rather unpleasant £70). Unfortunately, this didn't help. The CPS is apparently responsible for reading engine revs, so it may not be a coincidence that I don't see any revs on the dash when cranking the engine - possibly the CPS wiring or mounting is dodgy. Speaking of the CPS mounting, it turns out that the previous owner managed to snap off the bolt securing the CPS, then attempted (badly) to drill it out, and finally gave up and used a cable tie:
Why do it properly when a cable tie will just about do?
After a long conversation with the international technical advisory board, one of whom is currently located somewhere in the Arctic Circle, we decided that we still suspect the CPS, with the immobiliser being the second most likely candidate (less likely because it cranks OK - I think if it had had an immobiliser, then the starter wouldn't run). More investigation tomorrow.
Fortunately, Jason provided some good news: his exhaust is ready and seems good, so mine shouldn't be long now. It looks very shiny:
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Hi Dave,
ReplyDeleteI've got some screw extractors if you want to borrow them, and a M6 heli coil kit to put new threads in if its about that size for your CPS.
thanks... although despite mocking the previous owner's bodge, I'm probably going to do the same. Getting a drill in there would require removal of the cylinder head - it would all be a massive pain. What I really need is some tips on making engines start... got any bright ideas? I'm a bit stuck :-(
ReplyDeleteMaybe a pc based diagnostic program would be a way to go.. it would be useful for tuning the engine as well..I think a company called "carsoft" sells one for BMW (http://www.dealextreme.com/details.dx/sku.16549)
ReplyDeleteJust the usual, make sure there's a spark at the plugs, fuel being delivered and the timing is set correcty. You may need to check the fuel system has the right pressure, the tools for that job are expensive, but if it's wrong the car will not start according to a RAC man.
ReplyDeleteJohn: way ahead of you there, I've ordered something similar from Ebay (can't get Carsoft for a sensible price over here) - hopefully that will tell me what the problem is.
ReplyDeleteAustin: there's no spark and, after it primes, no voltage at the fuel pump, so it looks like the ECU isn't willing to start the engine. Haven't looked into timing - going to wait for the debug tools to (hopefully) tell me what's wrong before fiddling with bits of engine that I don't understand. Might do this at some point, but hoping not to go there yet.
I am guessing the ECU is looking for a signal from a sender unit (oxygen sensor is my guess from 3000 miles away) and in not recieving that signal, shuts the pump/spark down. Your software that connects to the ECU will show which unit it is either not receiving the signal from or the wrong signal.
ReplyDeleteThe ECU is just doing it's job of stopping the engine from damaging it's self, if something is wrong. Hope the diagnostic program can help.
ReplyDeleteDave, Sounds a royal pain.
ReplyDeleteCan you run through the sequence that does happen ? key in, at each position what works ? then what you know happens ?
Presume all things connected ? MAF/AFM etc.
Richard: key in, turn to first position. Fuel pump primes for two seconds, lights come up on the dash, etc. After priming, there is no further power to the fuel pump. Turn to ignition position: engine cranks but doesn't fire (still no power to the pump, and no spark). Crank position sensor is reading a nice clean square wave, no clear signal from cam sensor.
ReplyDeleteSoftware says it's immobiliser and cam sensor... immobiliser-free ECU is in the post. Hopefully that will get me to a point where I can start up. I'll post more details when it arrives.