T350 Electrical Problem
Discussion
Hello everybody. I hope somebody with automotive electrical know-how can help me out here. I managed to get moisture or water into my fuse box or somewhere in the electrical system. Sometimes the fan stays on with no ignition or the dash pod stays on with no ignition. If i just tapped the offending fan relay the fan would stop. If I took the dash pod fuse out and then put it back in the dash pod would stay off. I’ve put up with this for a few months now. It didn’t happen every single time I drove it. Just every now and again. Anyway, I decided to use a compressor with an air gun attachment and try to blow out any moisture in the fuse box. Then I drove off. About 3 minutes later the car cut out. I couldn’t start it. It would turn over but not start. I realised that the fuel pump wasn’t priming. I managed to push the car to a safe place. I got hold of a cheap 5 pin relay from Halfords in the same formation as the correct fuel pump relay and plugged it in. When you turn the key the fuel pump and the power steering pump continuously runs. It doesn’t stop after 2 seconds. The car starts no problem. I have since bought the correct fuel pump relay and plugged that in. Nothing happens. The fuel pump does not prime. The engine will turn but not catch. It will only start with the cheapo Halfords relay. Apparently it’s not good for the fuel pump to continuously run after you turn the ignition on. I took the fuse box out and completely took it apart and cleaned every single contact and dried it out. I put the fuse box back in the car but I’m still getting the same problem. What on earth could be going on here? How can I start the car with the wrong relay and not the correct relay? What should I be checking for to rectify this situation? Any help would be greatly appreciated.
Are you sure it's the fuel pump and not the power steering? I believe that the whirring sound when you switch on the ignition is the PAS - but I might be wrong. As far as I'm aware the fuel pump should be permanently energised by it's relay when the ignition is on.
When the relays get wet they can fill up with water as they are mounted upside down. Take each relay out (one at a time and remember where it goes back) and carefully prise off the plastic cover to see if it's full of water. Dry them out as necessary then see if it all works.
Nick
When the relays get wet they can fill up with water as they are mounted upside down. Take each relay out (one at a time and remember where it goes back) and carefully prise off the plastic cover to see if it's full of water. Dry them out as necessary then see if it all works.
Nick
Thanks for your reply, Nick. To be honest, I think what I’m hearing is the power steering pump continuously running. But only when I have the Halfords, cheapo, incorrect relay plugged into the fuel pump relay position on the fuse box. If I use the brand new correct relay I hear nothing at all and it won’t start. It just turns over. The fuel pump should energise with the ignition and then prime for about 2 seconds. Then turn off.
Edited by martin996uk on Thursday 30th November 18:51
Thank you for posting the images
If you look closely at the Halfords relay you will notice that one of the contacts is 87a and that contact is always in contact with terminal 30 until the relay is energised, the Halfords relay is nothing like the Bosch relay that has 2 x terminal 87's that both connect to terminal 30 when the relay is energised
In fitting the incorrect Halfords relay you are bypassing the relay switching circuit just like you would be if using a link wire to join terminal 30 to 87
There is a definite fault in the relay switching circuit that you are bypassing by using an incorrect relay
If you look closely at the Halfords relay you will notice that one of the contacts is 87a and that contact is always in contact with terminal 30 until the relay is energised, the Halfords relay is nothing like the Bosch relay that has 2 x terminal 87's that both connect to terminal 30 when the relay is energised
In fitting the incorrect Halfords relay you are bypassing the relay switching circuit just like you would be if using a link wire to join terminal 30 to 87
There is a definite fault in the relay switching circuit that you are bypassing by using an incorrect relay
Edited by Penelope Stoppedit on Thursday 30th November 22:35
Good morning
You mention that water got into your fusebox or electrical system, yes I can see the rusty relay bracket but that could be caused by condensation on cheap bad metal hence it possibly proves nothing. Do you know that lots of water was present around the fusebox area and very likely got into it?
With you mentioning about the fans and ignition sometimes staying on, there is a good possibility that moisture/water has got into the relays. As you no doubt know water will corrode relays and cause them to stick open or closed, sometimes moisure in a relay will conduct enough voltage to hold a relays contacts in once they have been pulled in by their conrol circuits.
Sorry I was tired last night and it didn't register with me that you have the fusebox disconnected and out
Before doing anything else
1) Slowly slowly take the covers off all of the original relays and have a good look to see if they have been damaged by moisture or had moisture/water in them that has now dried out, those metal relays covers are crimped around the relay bases and will prise open and squeeze closed later if you want to re-use them if good
2) Take a very close look with good lighting to see if any of the fusebox harness plugs terminals are corroded, discoloured or have been over-heating/melting
3) Take a very close look with good lighting to see if any of the fusebox terminals are corroded, discoloured or have been over-heating/melting
Considering that the car was a runner until you blew the fusebox out, there is obviously a great chance that something inside it is wrong but on the other hand coincidence could have raised its ugly head
The fuel pump relay should initially be getting a timed switch on signal from the Engine ECU and it does seem to be missing that signal
I will carry on here regardless of the results from your inspections above as it may save you waiting for me to reply to your findings
4) Take note and remove all the fuses and relays from the fusebox front, now look carefully at the rear of the fusebox to see if there are any brass/metal bus bars/links inserted anywhere, and remove them after noting their positions (there may not be any), do the same with any jumper plugs with cables (there may not be any)
Closely look at how the fusebox plastic front and rear cases are clipped together and slowly slowly prise the clips and the cases apart, you will need to work all the way around the cases until they finally come apart. Dont worry about the odd broken clip
You will now be able to carefully inspect the fuseboxes circuitry and may well have the problem staring you in the face, look at the terminals that grip the fuse blades and everywhere else
Although nothing at this stage in time apart from using air pressure (this does speak volumes) suggests that the fusebox is the cause of the problem, there is a very good chance that the fusebox is at fault and it is important to check out the fusebox internals if water has been getting at it
I will check back here later today
I have edited this by adding - I have just noticed the moisture marks below the long run of fuses
You mention that water got into your fusebox or electrical system, yes I can see the rusty relay bracket but that could be caused by condensation on cheap bad metal hence it possibly proves nothing. Do you know that lots of water was present around the fusebox area and very likely got into it?
With you mentioning about the fans and ignition sometimes staying on, there is a good possibility that moisture/water has got into the relays. As you no doubt know water will corrode relays and cause them to stick open or closed, sometimes moisure in a relay will conduct enough voltage to hold a relays contacts in once they have been pulled in by their conrol circuits.
Sorry I was tired last night and it didn't register with me that you have the fusebox disconnected and out
Before doing anything else
1) Slowly slowly take the covers off all of the original relays and have a good look to see if they have been damaged by moisture or had moisture/water in them that has now dried out, those metal relays covers are crimped around the relay bases and will prise open and squeeze closed later if you want to re-use them if good
2) Take a very close look with good lighting to see if any of the fusebox harness plugs terminals are corroded, discoloured or have been over-heating/melting
3) Take a very close look with good lighting to see if any of the fusebox terminals are corroded, discoloured or have been over-heating/melting
Considering that the car was a runner until you blew the fusebox out, there is obviously a great chance that something inside it is wrong but on the other hand coincidence could have raised its ugly head
The fuel pump relay should initially be getting a timed switch on signal from the Engine ECU and it does seem to be missing that signal
I will carry on here regardless of the results from your inspections above as it may save you waiting for me to reply to your findings
4) Take note and remove all the fuses and relays from the fusebox front, now look carefully at the rear of the fusebox to see if there are any brass/metal bus bars/links inserted anywhere, and remove them after noting their positions (there may not be any), do the same with any jumper plugs with cables (there may not be any)
Closely look at how the fusebox plastic front and rear cases are clipped together and slowly slowly prise the clips and the cases apart, you will need to work all the way around the cases until they finally come apart. Dont worry about the odd broken clip
You will now be able to carefully inspect the fuseboxes circuitry and may well have the problem staring you in the face, look at the terminals that grip the fuse blades and everywhere else
Although nothing at this stage in time apart from using air pressure (this does speak volumes) suggests that the fusebox is the cause of the problem, there is a very good chance that the fusebox is at fault and it is important to check out the fusebox internals if water has been getting at it
I will check back here later today
I have edited this by adding - I have just noticed the moisture marks below the long run of fuses
- *******Once the fusebox is in bits and you have checked it over - Please don't reassemble the fusebox until we have communicated on your findings as there will possibly be other testing needed**********
Edited by Penelope Stoppedit on Friday 1st December 10:30
I took the fuse box apart a few days ago. Completely apart. I had about 6 layers of fuse boards sitting next to each other. I used some contact cleaner on all the contacts. I could see a small amount of water had got in somewhere. Nothing major though. I opened up all the relays yesterday and they all looked fine to me. 
That’s a picture of the start of me taking the fuse box apart. I wish I had taken more pictures after that.
That’s a picture of the start of me taking the fuse box apart. I wish I had taken more pictures after that.
I can't find a diagram anywhere that will help with this
To be able to check out the fusebox properly and get the pinouts of the fusebox plugs so as to be able to check out the failing circuits properly, you will need to dismantle the fusebox unless you can get a diagram
With the fusebox dismantled you will be able to test from the relay/relays and fuses to the inputs and outputs terminals at the rear and also then have a drawing of the circuit so that you can test it all through once reassembled, continuity testing from the rear terminals to relay/relays and fuses with a 21 Watt bulb and a battery may well show the fault
This is a little like reverse engineering, you are starting at the end to get information so as to be able to test back to the beginning
I take it you know the fusebox is fitted to Porsche 911 models Year 1999 or thereabouts
I do wish you had mentioned that you had split the fusebox as it would have saved me much precious time
To be able to check out the fusebox properly and get the pinouts of the fusebox plugs so as to be able to check out the failing circuits properly, you will need to dismantle the fusebox unless you can get a diagram
With the fusebox dismantled you will be able to test from the relay/relays and fuses to the inputs and outputs terminals at the rear and also then have a drawing of the circuit so that you can test it all through once reassembled, continuity testing from the rear terminals to relay/relays and fuses with a 21 Watt bulb and a battery may well show the fault
This is a little like reverse engineering, you are starting at the end to get information so as to be able to test back to the beginning
I take it you know the fusebox is fitted to Porsche 911 models Year 1999 or thereabouts
I do wish you had mentioned that you had split the fusebox as it would have saved me much precious time
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