Help please. My R129 won't start.

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Joined
Sep 22, 2010
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Hello there.
I'm quite new to this forum & would be grateful for any help whatsoever.
My 1992 R129 SL500 refuses to start.
I've been trying for 3 weeks now but still no joy.
The car hasn't had a run out for some time due to I'll health but was started up last year a few times by my son and the engine run sweet.
However when I've come to it this year it just won't fully fire.
There is spark to all the plugs and fuel is getting through, however there is a strong smell of petrol from the exhaust.
I'm getting closer to it running as it is now running for 2 or 3 seconds then cutting out.
There are three lights on the dashboard for ASR, but that's always been on. But there are also lights for seatbelt warning & battery. Even though I've just put a new battery on.
It's also just started chiming from the drivers seat.
It wasn't doing this before when it wouldn't start.
I would be unbelievably grateful if someone could help as at the moment it's the one thing that I'm desperate to sort out as I've never really had time to enjoy the girl through ill health and would love to do a proper road trip in her.
Thanks so much for your time.
All the best & stay safe.
Glyn.
 
If you have ascertained you have a fuel and a spark then thats a good start, sounds like you`ve flooded your bores, be careful that you dont get bore wash, you may have stuck piston rings as its been standing so long, i would pop out all the plugs , quick squirt in each bore with wd40 and leave over night, any un-burnt fuel will evaporate, next day turn it over to clear the bores & pop plugs back in and try to restart, do not touch throttle pedal.

If it starts then fresh oil & filter will be a good idea

Failing that, it needs to be plugged into a scanner in case any new fault codes are apparent, or some old ones may need clearing.
 
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The car hasn't had a run out for some time due to I'll health but was started up last year a few times by my son and the engine run sweet.

You haven't said how long it's been laid up for under this regime - this is important as it'll allow us to gauge the overall situation. Has it been garaged or parked outside? Has the car been jump started at all?

This is not great for the early cars with distributors, as it doesn't generally get hot enough for long enough to burn off moisture inside the distributor caps. Take them off, wipe them out and remove any buildup on the contacts. Depending on age you may have to replace them.

Strong smell of petrol from the exhaust is standard during a heavy misfire on these engines. The M119 will still run apparently happily on an 11:1 AFR even though it's way off optimal.

Chime from the seat alarm could mean it's not latched (or the car thinks it's not latched), or it's aligned with the rest of the warning lights. OVP relay perhaps?
 
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You may have a fuel pump relay problem- its two stage 1rst primes the system on switch on 2nd needs an engine running signal to continue to power the pump/s [ a fire safety feature] - just ONE POSSIBILITY that might fit your symptoms
 
I think that 1992 was the last year of the CIS fuel injection system which does not like sitting as old fuel can gum up the system. I'm not sure if that's your problem because you have not told me enough about the car. I'm not even sure if the UK uses ethanol which further complicates matters but I suggest that you start with the basics.
Why don't you pour a little fuel in the intake (abut a 100ml) and see if it runs longer. That will tell you if the car has spark or is starved from fuel at the injectors and only the cold start is working.

As common sense would suggest, keep a fire extinguisher handy when playing with gasoline.
 
Hello there Sicario & Greenmanslk.
Thanks so much for your replies, very much appreciated.
I've had the plugs out & run the engine with them out and started from fresh again but still won't go.
There does seem to be equal compression from all 8 cylinders.
I've also put new plugs in.
There is allot of fouling of the plugs when I take them out.
I've also been starting it with no throttle whatsoever due to the strong smell of fuel from the exhaust.
The car will start with easy start but won't run without it.
The car is now ticking over for 2 or 3 seconds when it does fire, but then dies.
I will take the plugs out again & try the WD40 down the bores and hope that works.
Thanks again so much for your time and help.
Glyn.
 
If it fires than dies after a short while, could it be a faulty MAF (Mass Air Flow) sensor?
 
Hello there Grober.
Thanks for your reply.
I can hear the fuel pump activating/priming before I fully turn the ignition.
Not sure about the secondary charge though.
I'll try & get the lad to have a listen when I get him round.
Cheers pal, much appreciated.
All the best.
Glyn
 
You haven't said how long it's been laid up for under this regime - this is important as it'll allow us to gauge the overall situation. Has it been garaged or parked outside? Has the car been jump started at all?

This is not great for the early cars with distributors, as it doesn't generally get hot enough for long enough to burn off moisture inside the distributor

Hi Doodle.
Thanks for your reply.
The car has been sat for some time to be honest.
It has been in a well heated garage for the time it's been sat but yeah its probably a good 6 or so years since she had a good run out.
We did try to jump start her before I got the new battery.
I've had the dizzy's & rotor arm's of and give them a proper good clean, even though they weren't that bad to be honest.
The chime from the seat has only started yesterday.
Thanks again pal & all the best.
Glyn.
You haven't said how long it's been laid up for under this regime - this is important as it'll allow us to gauge the overall situation. Has it been garaged or parked outside? Has the car been jump started at all?

This is not great for the early cars with distributors, as it doesn't generally get hot enough for long enough to burn off moisture inside the distributor caps. Take them off, wipe them out and remove any buildup on the contacts. Depending on age you may have to replace them.

Strong smell of petrol from the exhaust is standard during a heavy misfire on these engines. The M119 will still run apparently happily on an 11:1 AFR even though it's way off optimal.

Chime from the seat alarm could mean it's not latched (or the car thinks it's not latched), or it's aligned with the rest of the warning lights. OVP relay perhaps?


Hi Doodle.
Thanks for your reply.
The car has been sat for some time to be honest.
It has been in a well heated garage for the time it's been sat but yeah its probably a good 6 or so years since she had a good run out.
We did try to jump start her before I got the new battery.
I've had the dizzy's & rotor arm's of and give them a proper good clean, even though they weren't that bad to be honest.
The chime from the seat has only started yesterday.
Thanks again pal & all the best.
Glyn.
 
Hello again all.
Don't know if its relevant but when I lock/unlock the car ig seems to take an age for the boot to lock/unlock and you can hear the hiss for a good 6/7 seconds.
Also the light beside the boot lock will only flash bright red when locked and a dim red when unlocked.
Thanks so much to everyone for the posts.
Glyn.
 
Hold off on the wd40, if it only starts with easy start then fuel is the issue, if it runs for 3 seconds that rules out spark as it wont run without a spark, obviously. The answer has to be either stale fuel/clogged injectors, or some safety system cutting in because of the stale fuel/clogged injectors. Your ecu might be detecting excessive DET (pre detonation) because of the fuel quality, Im assuming your battery voltage is sufficient, even though its a new battery it needs to show 12.7 volts when resting.

Disclaimer:- im no expert im just thinking what i would do in your place, process of elimination
 
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Although it is a new(ish) battery, have you checked it under load? IIRC, it should read c14volts but no doubt someone will correct that
 
Hi all.
This is the battery that I've bought.
Also I probably should of mentioned that it will now start & run for 2/3 seconds on fuel alone.
Thanks again guys, I've discovered way more on hear than any other forum.
You've all been so helpful.
Glyn.Screenshot_20200519-173820_Samsung Internet.jpg
 
Hello there again.
I was thinking it might be the injectors.
Does anyone know a good place the purchase them from please as I'm guessing there's not allot I could do with them.
Thanks again guys.
Glyn.
 
That looks like the right battery for your car. If your car starts by spraying ether into the intake or gasoline then you don't have a spark issue. As I suggested earlier, get a little bit of gasoline and pour it into the intake to get it running and keep dribbling fuel bit by bit to see if it will continue running. This will eliminate some guess work around whether it's ignition related / immobilizer etc.

Is the engine in post #14 your engine? If so, it's not CIS , it's the later EFI engines which had wiring harness issues. CIS cars had a fuel distributor with hard steel lines going to the injectors.

Before you buy injectors, you need to determine which injection systems you have.
 
Are new injectors diyable? Aren’t they pressurised?
 
I put that pic up in post 14 as according to Wiki thats the engine he should have

Just a thought, thinking about the engine and car being stood for so long, i would get a can of spray white grease and pop off every multi-plug connector i can see and giving each one a squirt
 

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