500SL 1990 R129
Discussion
Hi Everyone
Just got onto this site trying to sort out my Mercedes R129.
Car is running very lumpy , brought new H T leads and replace them all . 2 years ago i put new distributor's and plugs
After replacing the leads it was still running lumpy and backfiring ..
Now i cant start it.... Keeps trying to backfire
anyone have any suggestion's
regards
Billy59
Just got onto this site trying to sort out my Mercedes R129.
Car is running very lumpy , brought new H T leads and replace them all . 2 years ago i put new distributor's and plugs
After replacing the leads it was still running lumpy and backfiring ..
Now i cant start it.... Keeps trying to backfire
anyone have any suggestion's
regards
Billy59
Was it also running roughly when you replaced the plugs and distributors, is that why they were changed? Unless you can identify a point at which it suddenly started behaving differently, you're going to have to go back to basics re checks.
Are the distributor caps dry/clean inside? Any hairline cracks? I might be wrong but seem to recall that that these were susceptible to moisture?
Obvious checks are that the leads are fitted correctly, try refitting the old leads, does that alter anything.
Are the distributor caps dry/clean inside? Any hairline cracks? I might be wrong but seem to recall that that these were susceptible to moisture?
Obvious checks are that the leads are fitted correctly, try refitting the old leads, does that alter anything.
The new distributers was done by a mechanic about 2 years ago so all I've done is clean the insides of the caps
It was running rough about a year ago turned out to be cylinder 8 h t lead
2 months ago it was running rough again .so i brought a complete brand new H T lead replacement with plugs
Still running rough found one of the leads to the coil was duff. changed that put the old one back on still no change
When it was running after i changed the leads keeps backfiring manage to get it down in the car park
Now it will not start it feels like it trying to backfire. when it was running rough before sometimes there was a bubbling sound losing compression then it would pick-up again .
I've checked the leads and they go to the right cylinder and i put a meter across to make sure there good
Any suggestions
It was running rough about a year ago turned out to be cylinder 8 h t lead
2 months ago it was running rough again .so i brought a complete brand new H T lead replacement with plugs
Still running rough found one of the leads to the coil was duff. changed that put the old one back on still no change
When it was running after i changed the leads keeps backfiring manage to get it down in the car park
Now it will not start it feels like it trying to backfire. when it was running rough before sometimes there was a bubbling sound losing compression then it would pick-up again .
I've checked the leads and they go to the right cylinder and i put a meter across to make sure there good
Any suggestions
I had terrible problems trying to get mine started after being in long term storage.
I did the usual checks of the distributor caps, leads, plugs and OVP relay all to no avail.
It transpired that the issue was a combination of intermittent problems with the old Mercedes Dealer fit alarm and the ECU.
To finally fix the issue, the specialists who were recommissioning the car removed the alarm immobiliser system (which was temperamental at the best of times), and swapped in a reconditioned ECU.
Needless to say this wasn’t cheap, but means that the car now starts and is usable.
I appreciate this is probably not what you want to hear, but it seems that lack of use tends to dry out joints etc on the older style electrics. I have similar quirks with other electrical items on the car.
Like yours, mine is a 1990 500SL.
I did the usual checks of the distributor caps, leads, plugs and OVP relay all to no avail.
It transpired that the issue was a combination of intermittent problems with the old Mercedes Dealer fit alarm and the ECU.
To finally fix the issue, the specialists who were recommissioning the car removed the alarm immobiliser system (which was temperamental at the best of times), and swapped in a reconditioned ECU.
Needless to say this wasn’t cheap, but means that the car now starts and is usable.
I appreciate this is probably not what you want to hear, but it seems that lack of use tends to dry out joints etc on the older style electrics. I have similar quirks with other electrical items on the car.
Like yours, mine is a 1990 500SL.
Deefor62 said:
I had terrible problems trying to get mine started after being in long term storage.
I did the usual checks of the distributor caps, leads, plugs and OVP relay all to no avail.
It transpired that the issue was a combination of intermittent problems with the old Mercedes Dealer fit alarm and the ECU.
To finally fix the issue, the specialists who were recommissioning the car removed the alarm immobiliser system (which was temperamental at the best of times), and swapped in a reconditioned ECU.
Needless to say this wasn’t cheap, but means that the car now starts and is usable.
I appreciate this is probably not what you want to hear, but it seems that lack of use tends to dry out joints etc on the older style electrics. I have similar quirks with other electrical items on the car.
Like yours, mine is a 1990 500SL.
According to the MB website a dodgy immobilser will stop the car turning over rather than failing to start. I did the usual checks of the distributor caps, leads, plugs and OVP relay all to no avail.
It transpired that the issue was a combination of intermittent problems with the old Mercedes Dealer fit alarm and the ECU.
To finally fix the issue, the specialists who were recommissioning the car removed the alarm immobiliser system (which was temperamental at the best of times), and swapped in a reconditioned ECU.
Needless to say this wasn’t cheap, but means that the car now starts and is usable.
I appreciate this is probably not what you want to hear, but it seems that lack of use tends to dry out joints etc on the older style electrics. I have similar quirks with other electrical items on the car.
Like yours, mine is a 1990 500SL.
RJG46 said:
According to the MB website a dodgy immobilser will stop the car turning over rather than failing to start.
Mine was definitely turning over, and the immobiliser was linked to the fuel pump relay hence it not firing. When the system was working, you had to start the car within 30 seconds of opening, else the immobiliser kicked in. Had many an embarrassing moment at petrol stations when I wasn’t quite quick enough.
I understand that the old alarms are a common problem, and that they are often taken out to resolve starting issues.
I was amazed at the amount of wiring and other assorted paraphernalia that was removed.
I think it was a Scorpion alarm which was a dealer fit at the time.
Good luck in getting to the root of your issues.
I was amazed at the amount of wiring and other assorted paraphernalia that was removed.
I think it was a Scorpion alarm which was a dealer fit at the time.
Good luck in getting to the root of your issues.
A bubbling sound and losing compression - as per post on Tues. Bubbling sound where? If so, that could be a number of things. Any sign of coolant loss, weeping from the base of the cylinder heads? Any sign of coolant in the oil, or oil in the coolant.
Were the plugs the correct type and correctly torqued, ie you don't have one or more that aren't correctly seated/sealed.
From what you've said, ie running 2 months ago, I presume that the petrol is not really old and hasn't gone off.
Are you able to hear the fuel pump priming when ignition is turned on, or can you check feed to it? The fact that it's been running and still tries to tends to point away from immobilsers etc. for me.
Air filter, clean? It's not unknown for rodents to block them if car's been left standing for any period of time, I saw one only a few months ago, dead mouse and a real mess inside the air filter housing (not an SL500 though).
There will be numerous sensors, ie crank sensor (which I presume that engine has), all of which can affect fueling etc etc, might be worth locating and cleaning contacts with electrical cleaner.
Were the plugs the correct type and correctly torqued, ie you don't have one or more that aren't correctly seated/sealed.
From what you've said, ie running 2 months ago, I presume that the petrol is not really old and hasn't gone off.
Are you able to hear the fuel pump priming when ignition is turned on, or can you check feed to it? The fact that it's been running and still tries to tends to point away from immobilsers etc. for me.
Air filter, clean? It's not unknown for rodents to block them if car's been left standing for any period of time, I saw one only a few months ago, dead mouse and a real mess inside the air filter housing (not an SL500 though).
There will be numerous sensors, ie crank sensor (which I presume that engine has), all of which can affect fueling etc etc, might be worth locating and cleaning contacts with electrical cleaner.
New Plugs------ was running bad with the old and new
New Cam Sensor will look at the crank sensor
Fuel pumps working ok when ignition is turned on
The Bubbling sound only appears when i was trying to put my foot down on the gas when it was running lumpy
Going to see a mechanic today thats worked on a lot of old r129s
Thanks everyone
New Cam Sensor will look at the crank sensor
Fuel pumps working ok when ignition is turned on
The Bubbling sound only appears when i was trying to put my foot down on the gas when it was running lumpy
Going to see a mechanic today thats worked on a lot of old r129s
Thanks everyone
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