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Hi Guys
my problem started after a 10 mile run on the highway and all was going well until I went around a roundabout to come back home, nothing major but just a couple of cut outs as I was turning sorta like the car switched off for a split second. Was fine on the return trip until exiting the off ramp when the car died and coasted to the curb, the started straight away but did the same coming around the corner to home. Have taken it around the block twice since and the last time it only just made it to the garage and had to push it in.
the car will only start after a lot of cranking and only for about 5 seconds on not many cylinders I think.
the car had old fuel which I have now drained and replaced, checked the fuel pump and the rails have and hold pressure. I have removed all the injectors and cleaned them and checked the flow and they all switch.
last night I pulled a plug and expected it to be wet but it is dry and very black. I checked the spark and it doesn’t seem as strong as I have seen on other cars, more of a orange spark instead of blue.
should I somehow check that my injectors are getting a signal and if so how please so that I can eliminate fuel, and should the plug be wet from trying to start the car
thanks
What you're describing could be electrical but could also be a fuel delivery issue with a failing pump, clogged pump, or clogged filter.
I checked the pump and it had good flow where I disconnected the line at the rails so I think everything downstream of that is good. I haven’t checked from there to the injectors so I will check it tomorrow just so I can give the fuel delivery a tick, although I could not see there bring a blockage there. I ordered a noid light today so will check the he signal to o the injectors as soon as it arrives
I checked the pump and it had good flow where I disconnected the line at the rails so I think everything downstream of that is good. I haven’t checked from there to the injectors so I will check it tomorrow just so I can give the fuel delivery a tick, although I could not see there bring a blockage there. I ordered a noid light today so will check the he signal to o the injectors as soon as it arrives
What SEEEEMs like good fuel flow might not be. Ask me how I know. It's when it's under pressure and needs to be, consistently, tells more...
Sounds like fuel or electrical as well, as was said.
I had a similar issue a few months ago, went over a bump and engine cutout briefly and did it multiple times on the way home. Cleaned the ground connections and hasn't happened since.
What SEEEEMs like good fuel flow might not be. Ask me how I know. It's when it's under pressure and needs to be, consistently, tells more...
Sounds like fuel or electrical as well, as was said.
Jay I think what your saying is worth investigating as Im guessing the flow is only about 6 litres a minute from the amount of time it took to fill a 1250 ml soda bottle. I will do it again to get an accurate measurement.
Also while there was pressure at the rail I was expecting a bit more
My '84 US model would shut off on me instantly after driving for a bit a few years back. Turned out to be a bad fuel injection relay (#16) that would fail to open when it got warm. Not sure how that would be related to shutting off in turns but it's a cheap fix to try.
For this model there are three relays that are required for the engine to run, the fuel pump, LH and EZF relays. If any of these fail the engine will stop running. It is a good idea to replace these relays every 10 to 20 years. Many are probably going on 30 or more years.
For this model, and newer 928s, these relays are the same as the horn relay (P/N 141.951.253.B). So in a bind, if the horn honks that relay can be substituted in those three sockets.
A bit of an update on mine to date, I am very busy with work atm so haven't had a lot of time with my no start issue
- changed the Fuel pump relay, EXK relay and the LH Jetronic relay with no change
- put a noid light on cylinders 1 & 5 and all ok
- checked spark at plugs 1 & 5 and all ok
- checked Temp 2 resistance block temp was 24 degrees C - 2.12 k ohms which seems ok
- Fuel flow at approx 4000 cc a minute which seems ok
- Spark plugs are not wet
- CHECKED FUEL PUMP PRESSURE WITH FUEL PUMP JUMPED - 62 PSI This seems high to me?
- PRESSURE INSTANTLY DROPPED TO ABOUT 10 AND THEN TO 0 IN 30 SECONDS AFTER TURNING PUMP OFF - Faulty check valve?
I checked the pressure before the fuel rails with a T type fitting that allows the fuel to flow through because I wasnt to keen to put to much pressure on the rail port cover as it was tight
Last edited by PaulCarrera; 11-01-2021 at 09:35 PM.
Yes I thought that and I am going to replace it along with the pump (carry the old pump as a spare)
Would this cause it to not start as I assumed that once the pressure was up it would start
The pressure seems too high as well I think its supposed to be around 36 PSI but maybe if it was running it would come down?
Yes I thought that and I am going to replace it along with the pump (carry the old pump as a spare)
Would this cause it to not start as I assumed that once the pressure was up it would start
The pressure seems too high as well I think its supposed to be around 36 PSI but maybe if it was running it would come down?
Yes, if you're losing that pressure it will also make the restart difficult.
10-18-2021, 07:17 PM
Start Problems
