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P38 troubleshooting


Simon_CSK

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Finally got my BeCM sorted and refitted to the car and was expecting to just put it in and it would fire up considering it drove into the current position. The key is synced to the BeCM and all dash lights appear to work but when I turn the key all I can hear from the BeCM is a click and nothing from the starter motor. 

Any ideas where to start looking?

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When you turn the key to position 2 do you get the usual messages in the message centre about windows not set etc. that always happen after battery disconnection? If not you may have a problem with the BECM itself.

Do you get an engine immobilised message in the message centre? If so could need re-syncing to engine ECU. If not immobilised then it should crank, so check basic things as for a "normal" car i.e. starter relay operating (RL16 I think in engine compartment fuse box).

You were asking before about the connections to BECM. The N wire is permanently live via MF4, the NLG wire is permanently live via MF1  and the NK wire is permanently live via MF5. Might be worth checking.

Above is from my 1996 GEMS P38, I assume later ones are similar.

Mike

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Position 2 is ok and get window messages etc.

Don't get the immobilised message was looking carefully for that one. 

Yes thanks for the photo it helped as I had cross wired to of the positives and that led to a plug I hadn't connected. If I have time I will take the BeCm out tomorrow and check all the plugs are in.

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Does the yellow check engine light come on? If the BECM is happy with the key it sends the de-immobilisation code to the engine ECU which if correct turns on (via the BECM) the check engine light.

So if you're not getting an immobilised message and the check engine light is on everything should OK as far as immobilisation goes. At least that how it works for GEMS, I assume Thor is similar? Which is yours?

Assuming the above is OK then  I would be checking basic stuff. You say you hear a click from the BECM when you turn the key, is that to position 3 (start)? If so that's probably the BECM internal relay trying to operate the starter via RL16 in the fuse box. I would be checking that at relay 16 to see if the is coil is energised when the key is in start position. You can then trace on from the relay to the starter motor or back too the BECM depending on what you find.

Mike

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The yellow light that looks like an engine block comes on yes'

Mine is Thor.

I did as you said and checked the relay RL16 (replaced it with one I had) and tried the key again. I could hear both the BeCM and the relay activating so power is getting to the relay. So now I need to see if the power is reaching the solenoid which should be an easy test just run a power lead from the solenoid to the battery and see if it starts.

 

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That's good, if RL16 is clicking you can discount the BECM. Remember just because a relay clicks doesn't necessarily mean it working, I've been caught by that before.

But as the relay is clicking there's not much else it can be. Try a link across pins 3 and 5 of the RL16 socket in the fuse box to see if it cranks.

You may have it but here is the starter wiring for a 1999 on from RAVE in case you haven't.

Starting.JPG.d18b4f0f4ed2ec6702e1c0510b650849.JPG

 

Mike

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Simon, I hope bridging the relay works and it's a simple fix.

For completeness, I'll share my experiences as well. We've fitted MegaSquirt to 2 P38s and both times had problems with the starter. At first it works, but after a couple of tries no signal from the BECM to the relay anymore. Possibly because it fails to get the feedback it expects from the engine ECU. I got around this by wiring the ignition switch directly to RL16 (C1278-6 to C1282-12 in the diagram above). I plan to do the same for the switched ignition feed, to make sure the car can still drive (i.e. MS gets power) should the BECM fail.

Before digging into the wiring, double check if the relay really is activating, for example by measuring voltage across pins 1 and 2 with RL16 removed.

Filip

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11 hours ago, Escape said:

Simon, I hope bridging the relay works and it's a simple fix.

For completeness, I'll share my experiences as well. We've fitted MegaSquirt to 2 P38s and both times had problems with the starter. At first it works, but after a couple of tries no signal from the BECM to the relay anymore. Possibly because it fails to get the feedback it expects from the engine ECU. I got around this by wiring the ignition switch directly to RL16 (C1278-6 to C1282-12 in the diagram above). I plan to do the same for the switched ignition feed, to make sure the car can still drive (i.e. MS gets power) should the BECM fail.

Before digging into the wiring, double check if the relay really is activating, for example by measuring voltage across pins 1 and 2 with RL16 removed.

Filip

Filip

Was working on it today there is 12v at 2 pins and when I bridged the relay between pins 85 and 86 which are the feed to the starter I got nothing. I got my son to operate the key and the relay is certainly getting a signal from the BeCM as it is clicking. Wired the output of the relay direct to live and again no change. If I get time tomorrow I will jack the car up and put a feed directly to the starter motor and see if it will crank.

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2 hours ago, Simon_CSK said:

Filip

Was working on it today there is 12v at 2 pins and when I bridged the relay between pins 85 and 86 which are the feed to the starter I got nothing. I got my son to operate the key and the relay is certainly getting a signal from the BeCM as it is clicking. Wired the output of the relay direct to live and again no change. If I get time tomorrow I will jack the car up and put a feed directly to the starter motor and see if it will crank.

The brown and red feed to the starter solenoid leaves the fuse box via the pink plug. Could be worth checking the connection is good at the fuse box end and that the spade connector at the solenoid is also still attached.

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9 hours ago, Escape said:

Those test rule out a lot, does seem to be starter motor or even more likely wiring.

@elbekko had the same problem a while back, turned out the spade at the starter motor had a bad connection (as above). Easy fix, luckily.

But why would it just suddenly fail at the same time as I had issues with the BeCM? Or am I just being stupid? 

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If the relay clicks/ gets 12V but the starter motor doesn't turn even with the relay bridged, it's hard to see how it could be the BECM. Maybe something simple like a wire that has been disturbed doing something else.

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2 minutes ago, Escape said:

If the relay clicks/ gets 12V but the starter motor doesn't turn even with the relay bridged, it's hard to see how it could be the BECM. Maybe something simple like a wire that has been disturbed doing something else.

Not had a chance the crawl underneath it yet, and have been playing with my RR Sport. Hope to get a look tomorrow afternoon so watch this space.

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What are the chances of a dodgy starter motor when it was parked up running but with an BeCM problem!! Is this car ever going to let me use her??

Have been under her this afternoon and I can categorically say that I have a problem with the starter motor. I put a spanner across the terminals to see if I could get it to crank and there were a few sparks. Go a light out and shone it up and had a closer look at the terminals and noticed that the braded cable from the starter to the solenoid has detached from the bolt fixing. I guess I need to change the starter before I try again.

 

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15 hours ago, Simon_CSK said:

What are the chances of a dodgy starter motor when it was parked up running but with an BeCM problem!!

High. These cars seem to thrive on neglect. The more you take care of them, the more they break.

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I have the car on stands now waiting for the Starter motor to appear. Once I have that fitted hopefully everything will be good to go and I can get it MOT'd for the summer. 

I am hopeful it will arrive tomorrow.

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OK guys looking good, put the new starter in this afternood but have lost a socket on the top hex bolt as I cannot get near it to remove it. Will retreive it the next time I have a starter issue. It was one B*gg*r of a job.

The car is now cranking but not firing. Given the issue was a rebuilt BeCM could that now be the BeCM not talking to the ECU?

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18 minutes ago, Simon_CSK said:

OK guys looking good, put the new starter in this afternood but have lost a socket on the top hex bolt as I cannot get near it to remove it. Will retreive it the next time I have a starter issue. It was one B*gg*r of a job.

I found it's a lot easier now I've removed the inner wheel arch :P

18 minutes ago, Simon_CSK said:

The car is now cranking but not firing. Given the issue was a rebuilt BeCM could that now be the BeCM not talking to the ECU?

Very possible. Should be able to see that with nanocom or similar.

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