J

johnnyb70

Well-Known Member
Hi all I'm an avid follower of this forum and have recently rebuilt my 4.6 gems. Anyway after several weeks getting it all back together I t runs great. I take it for mot it passes! I get cocky and go for a run 8miles go into a shop and the thing won't run well. Massively over fueling. After much diagnoses and recovery home I find a post from achap with similar symptoms whose cam sensor wires had worn he had fixed it but it still ran terribly. He found a track had burnt in the ecu! I take out the ecu and bingo a fried track that goes to the multi sensor pin(36) on the red connector 507. I'm guessing there must be a problem (short) on one of the sensors/wires connected to pin 36. I'm at my wit's end tbh. Ive already fried my original ecu and another one after I fixed a wire (O2 sensor) that didn't fix the problem. Can anyone help me. I'm getting better at reading wiring diagrams btw. I also need another ecu but until I find the problem 100per cent I'm not going to plug it in.
John
 
Thanks grrrrr how would I contact@martyuk. Or will he pick this up? I'm just contemplating my next move tbh. I've ordered another ecu to be prepared but I'm feeling I'll have to delve into the wiring loom. I think pin 36 provides the 5v reference to the resistor type sensors....could one of these sensors be faulty? Anyway grrr thanks for your reply I felt it may have been massively to technical to get a response!.
 
There is not much to do with a P38 that's out of the scope of members on here its just a case of the right ones picking up the thread:)
if you put your location up in your profile to see if local for peeps to help.
 
I'm from Biddulph nr Stoke btw. I remember a p38 owning mate who I've lost touch with mentioning a guy called Phil something who worked at Lucas rists on these vehicles working as mobile diagnostics he lived in Newcastle under Lyme somewhere.
 
If its just a burnt out track you can simply repair it with a bridging link, I suspect it started with a dry joint and just burnt threw.
 
hi, can you test the wire continuity from plug to plug with a metre? Just to make sure it's not earthing somewhere around the engine or chassis?
 
The cause is definitely external to the ecu as I found a bit of melted wire on the oxygen/knock sensor part of the loom replaced this put a bridging link in the ecu and it blew the next component along. I thought I found a short between the outside wires on the maf but these are connected via the cam sensor as when I unplugged the cam sensor I lost continuity. I will recheck from the plugs to the ecu though. It seems odd that the ecu isn't protected from a simple short somehow.
 
I've been testing continuity end to end of the red/black wire which has been fine and also to earth which has not bleeped.
 
I don't think it's the becm but I suppose the ecm and the becm must have a connection. I'll try to contact him as he sounds like he's Daman! Btw Lucas rists made all the wiring loom for p38 and jags etc. Still in Newcastle but now called leoni they do looms for Bentley amongst others. Thanks again
 
I would buy a gems engine loom and if one comes up on the bay I would but none for sale atm. The swap aside from routing would be straightforward and if cured my issue worth it.
 
He found the fault, he just needs to establish if this burnt track is a primary or secondry problem.
The gems ecu itself could be shorting out, but the rule of thumb is this, if the engine has had work & this fault is evident after the work, then go back to the work done.
The usual problem is a trapped / crushed wire, shorted connected etc.
The only way to really find out is to bite the bullit & plug another gems ecu in & see if the same fault replicates itself.

As for the old ecu, when you repaired the track, the wire or whatever you used to repair is of less resistence than the burnt track, hence, the next component in line took the brunt & popped.

The Gems ecu's failing is a common fail as these vehicles get older. I just replace the ecu as they're cheap enough to buy, & simple to program to the system.

I wouldn't put the Becm at fault here.
 
Hi Rick
Technically this is the third fried ecu (if you count my bridge repair). The fourth is on it's way via the bay. I suppose I can get 2 tries from every ecu I buy! I think I need to open up the loom to check the red black wire particularly around the splice. Could a faulty sensor cause this as well? Btw the first one stopped communicating when I tried to re program back to 4.6 auto from 4.0 manual during the wtf is going on here stage!
 
If you've already tried a replacement ECU, & that's also blown, then it's another problem, like the loom or such.
You will be the only person to solve this as you have the vehicle, & although this forum can guide you, it's just from guess work.
Check connectors & no bent pins inside, but it's certainly looking like a wiring issue.
 
Hi everyone that helped and posted I've solved the issue. After receiving an email back from Mr gems Marc Adams he suggested the only two places on an unmodified loom this can happen are.....cam shaft position sensor and the maf sensor areas of the loom. After much stripping back of protection I found the maf was fine(easiest to get to) I removed the belt tensioner and the alternator undid the cam position sensor and pulled the wire up stripped off all the protection then the now crispy tape and it felt a bit wet well damp. I sprayed it with cleaner and big roll, it was coolant I think. Must have got in there over 12 months ago when I stripped the heads been sitting there waiting for a crack( I couldn't see one the wiring was in good condition apart from where it was exposed at the ends) I guess manuveuring the loom caused a tiny crack(s) and wallop.) I put a bridging wire on my original ecu thinking I thought I'd corrupted it but I hadn't. it fired in and idled well.
What have I learnt.. don't go deep wading in 20year old electronic vehicles. Never lose heart at least if you do have patience and it'll come back! What a great guy Marc Adams is to reply to someone out of the blue is outstanding I think. His advice also made me think it could be fixed.
And you guys for making me feel I'm not on my own! I will commit to visit this forum once a week and help if I can.
Cheers
John
Ps I fitted yellow top mustang injectors and what an improvement over stock! Only £30 used from America(all 8). Highly recommended.and a perfect fit you need the steel body ones as they have the cutout for the injector clip.
 
johnnyb70 said:
Hi everyone that helped and posted I've solved the issue. After receiving an email back from Mr gems Marc Adams he suggested the only two places on an unmodified loom this can happen are.....cam shaft position sensor and the maf sensor areas of the loom. After much stripping back of protection I found the maf was fine(easiest to get to) I removed the belt tensioner and the alternator undid the cam position sensor and pulled the wire up stripped off all the protection then the now crispy tape and it felt a bit wet well damp. I sprayed it with cleaner and big roll, it was coolant I think. Must have got in there over 12 months ago when I stripped the heads been sitting there waiting for a crack( I couldn't see one the wiring was in good condition apart from where it was exposed at the ends) I guess manuveuring the loom caused a tiny crack(s) and wallop.) I put a bridging wire on my original ecu thinking I thought I'd corrupted it but I hadn't. it fired in and idled well.
What have I learnt.. don't go deep wading in 20year old electronic vehicles. Never lose heart at least if you do have patience and it'll come back! What a great guy Marc Adams is to reply to someone out of the blue is outstanding I think. His advice also made me think it could be fixed.
And you guys for making me feel I'm not on my own! I will commit to visit this forum once a week and help if I can.
Cheers
John
Ps I fitted yellow top mustang injectors and what an improvement over stock! Only £30 used from America(all 8). Highly recommended.and a perfect fit you need the steel body ones as they have the cutout for the injector clip.
Click to expand...
Glad to hear you got it fixed.
Those injectors from the states, would they work on a thor engine and in what way are they better?
 
I don't think they would improve on Thor injectors as they are made by Bosch as well. The mustang injectors are made by Bosch btw.
They are a much more modern design than the original Lucas injectors with an improved spray pattern. I think these type of mods are good because they improve the efficiency of the old lumps.win win.
In the gems they are plug and play.
I now think my injectors we're leaking fuel after 150000 miles as the improvement is so profound!
I have Lucas injectors in my xjs and they are fine though.
 
You must log in or register to reply here.

Similar threads

O
03 L322 EAS ECU Can bus fault / ABS temp system deactivation
Replies
1
Views
622
oldradiotech
O
R
Range Rover Supercharged Oxygen sensor 3 problem
Replies
14
Views
2K
biketeacherdave
biketeacherdave
JT_spark
P38 DSE Auto intermittent lack of power after vehicle has been hot
Replies
8
Views
548
brianp38dse
brianp38dse
D
Range rover p38 dse none egr
Replies
8
Views
336
Grrrrrr
Grrrrrr
K
Range Rover 2008 tdv8 auto - Part help!
Replies
3
Views
688
Graculus
Graculus