Can anyone offer any tips .Drove my car into the garage left it for a week.Nice day decided to take it out but alas it would not start.Plenty life in the battery,Engine turning ok, half a tank of fuel.when i turn the ignition on fuel pump does not cut out after a few seconds as it normally would.Could this be the fuel pump relay and if it is can any one tell me where to find it as it does not apear to be in the engine compartment or in the luggage.Car is a 1984 3.2 carrera cabrio.Many thanks Liam.
car wont start
- Thread starter l2015
- Start date
Helen Goff
No.1 Poster
are you sure there is "plenty of life" in the battery in my experience Porsches need a frightening amount of power to kick the car into life.
adamtsobek
New member
Hi
Similat thing happened to me about a month ago, had to call out the AA patrolman.
It took him just 5 mins to find the fault. Prior to him coming I checked the usual things but could not find the fault.
The AA asked me to turn the engine over whilst he checked the fuses and sure enough it was the petrol pump fuse that had broken inside the holder, so it looked OK but exploded when the AA were testing it.
Minutes later all was well and I was on my way
Adam
Similat thing happened to me about a month ago, had to call out the AA patrolman.
It took him just 5 mins to find the fault. Prior to him coming I checked the usual things but could not find the fault.
The AA asked me to turn the engine over whilst he checked the fuses and sure enough it was the petrol pump fuse that had broken inside the holder, so it looked OK but exploded when the AA were testing it.
Minutes later all was well and I was on my way
Adam
Just had a quick look at Bentley:
Possible causes of a no start/difficult start condition:
Ground or plug connection - check ground connections at intake runner 1, behind fuel filter. Check connections at fuel injectors, etc.
Reference (TDC) sensor faulty - test sensor with oscilloscope for 2.0v sine wave.
Ignition system fault - Test coil.
Air flow sensor faulty - Test air flow sensor.
Fuel pressure incorrect - check fuel pressure/pressure regulator.
DME cylinder head temp sensor faulty - test resistance at room temp (2.2 to 2.8 k-ohms)
Fuel injectors not working - check for at least 10v with key on at injector connector. Check for pulsed ground signal with engine running/cranking.
CO level and idle speed adjustments incorrect - check for vacuum leaks.
Possible causes of a no start/difficult start condition:
Ground or plug connection - check ground connections at intake runner 1, behind fuel filter. Check connections at fuel injectors, etc.
Reference (TDC) sensor faulty - test sensor with oscilloscope for 2.0v sine wave.
Ignition system fault - Test coil.
Air flow sensor faulty - Test air flow sensor.
Fuel pressure incorrect - check fuel pressure/pressure regulator.
DME cylinder head temp sensor faulty - test resistance at room temp (2.2 to 2.8 k-ohms)
Fuel injectors not working - check for at least 10v with key on at injector connector. Check for pulsed ground signal with engine running/cranking.
CO level and idle speed adjustments incorrect - check for vacuum leaks.
This sounds a bit like a recent failure at croft, where a 3.2 did the same thing. The on the ground diagnosis was that the impeller in the fuel pump had probably collapsed.
The pump was running, but no fuel arriving at the important end of the car, and hence no start.
The pump was running, but no fuel arriving at the important end of the car, and hence no start.
Fuel pump should cut out on pressure ?
If the pump is continuously running then is the pump not pumping ?, has a pressure reg failed and dumping fuel back to the tank not allowing the pressure to rise ?
The pump not cutting out is abnormal and I would suggest you start your investigations there.
Edited to add: Supersport, you beat me to it !
If the pump is continuously running then is the pump not pumping ?, has a pressure reg failed and dumping fuel back to the tank not allowing the pressure to rise ?
The pump not cutting out is abnormal and I would suggest you start your investigations there.
Edited to add: Supersport, you beat me to it !
3.2_fordy
Moderator
Liam
I was the 3.2 at Croft I found out the drive coupling had broken now fixed If you can hear the pump working its not your DME it may be a simler fualt as I had, but to check if the fuel pump is pumping you can just take off the pressure tap off nut on the left hand fuel rail dont loose the small ball in side the nut, get some one to quickly buss the motor over and put a small container to catch any fuel if any (be careful dont light a fag at this point) Email me offline if you want have had most of the fuel side to bits in the past
I was the 3.2 at Croft I found out the drive coupling had broken now fixed If you can hear the pump working its not your DME it may be a simler fualt as I had, but to check if the fuel pump is pumping you can just take off the pressure tap off nut on the left hand fuel rail dont loose the small ball in side the nut, get some one to quickly buss the motor over and put a small container to catch any fuel if any (be careful dont light a fag at this point) Email me offline if you want have had most of the fuel side to bits in the past
With my '84 MY sport coupe the fuel pump does not come on when you turn on the ignition. It will only come on when the engine is actually cranking.
You should hear the electronic extra air valve that helps control the idle consuming electric with the ignition on.
You can jump the fuel pump from the battery to its fuse in the luggage compartment, this will help you know whether you can hear the fuel being moved. As suggested, you could check for pressure in the engine bay although I think it is easier to loosen the connection on top of the fuel filter to check for fuel pressure. You will only need to loosen it to get fuel spraying out.
According to internet rumour, we should all carry a spare DME relay around with us. I got one this week!
You should hear the electronic extra air valve that helps control the idle consuming electric with the ignition on.
You can jump the fuel pump from the battery to its fuse in the luggage compartment, this will help you know whether you can hear the fuel being moved. As suggested, you could check for pressure in the engine bay although I think it is easier to loosen the connection on top of the fuel filter to check for fuel pressure. You will only need to loosen it to get fuel spraying out.
According to internet rumour, we should all carry a spare DME relay around with us. I got one this week!
many thanks for all your suggestions,had an auto spark check the car over today.After a few tests he reckons its a sensor.There is a vertical rail with 3 plugs in it opposite the fuel filter,the top plug is white, the middle one is black and marked BG and the bottom one is also black and marked DG{the electrician says the bottom one marked DG is faulty}.All three leads go from there and pass down through an aperture between the left air inlet manifold.After he worked this out I showed him a DME troubleshooting chart I had downloaded from pelican.The chart shows 2 sensors here.Engine speed sensor and reference TDC sensor, he was unable to workout from the chart which one was which.Next I called the parts department at porsche to see if they could tell me.They said the top one{white}is a timing mark sensor and the middle and bottom are the same and go to the crankshaft.If Anyone is still awake by now and has had to replace any of these can they let me know if this is an awkward job,looks hard for access to me with the engine in situ and judging by the electrician tryin 2 backheel it to a mate who works on 911s sounds quite time consumin.thanks all Liam.
Be careful of the main dealers, they know very little about our cars. I said to one a while back that I had a 930 and he didn't have a clue what I was talking about...
The white plugged sensor is actually CHT cylinder head temp sensor. The two black plugged senors are speed and reference sensors for timing (not sure which is which either). Also, if IRC they both have the same part no.
I sent you an email.
The white plugged sensor is actually CHT cylinder head temp sensor. The two black plugged senors are speed and reference sensors for timing (not sure which is which either). Also, if IRC they both have the same part no.
I sent you an email.
As I understand it there is a TDC sensor mounted near the flywheel, but it is NOT linked to the DME system and therefore does not affect the way the engine runs.
The DG sensor you mention is the engine speed sensor. BG is the reference sensor - this one supplies the DME system with the crankshaft reference signal.
The DG sensor you mention is the engine speed sensor. BG is the reference sensor - this one supplies the DME system with the crankshaft reference signal.
If you suspect you need a new clutch I would drop the engine assy and split the tranny from the engine.
You have to have a correct gap from the sensor to the flywheel, that would seem to be the tricky part to me while trying to do it from above.
You have to have a correct gap from the sensor to the flywheel, that would seem to be the tricky part to me while trying to do it from above.
Nathan,I raised the back of the car today, removed the rear wheel on the passenger side and found you can get access from here .Both the sensors are mounted on a bracket here.I decided to try a test run as it has to come off anyway,it wasnt too bad from here and I managed to remove them with a bit of perseverance.It looks as if the new one should go on as the old one came off,When the new sensor is fitted and secured to the mounting bracket and then onto the engine then hope fully that will remedy the problem.Cheers Liam
Yep, I had a look yesterday at mine. Just getting the gap right will be awkward. At least they are easy to get to. Makes a change to have something accessible [
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Guest
New member
liam,
Another member had the same problem and after many weeks of testing this and testing that and doing a shed load of work he found that although the fuel gauge said he had a healthy load of fuel in the tank he did not. The float had stuck, this has been reported in the Porsche post and is a common fault.
So to be sure put a couple of gallon in the tank before doing anything else and try again to start the car.
If this checks out OK and the car still will not start get a spare plug ( no need to take a plug out of the head) and connect it to a plug lead and lay it on the block and crank the car over to see if you have a spark.
Cheers
John
Another member had the same problem and after many weeks of testing this and testing that and doing a shed load of work he found that although the fuel gauge said he had a healthy load of fuel in the tank he did not. The float had stuck, this has been reported in the Porsche post and is a common fault.
So to be sure put a couple of gallon in the tank before doing anything else and try again to start the car.
If this checks out OK and the car still will not start get a spare plug ( no need to take a plug out of the head) and connect it to a plug lead and lay it on the block and crank the car over to see if you have a spark.
Cheers
John
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