'73 450 SL electronic fuel injection

[Alex Crow]

yup, the consensus then is that a jiggle/wiggle/prance is needed, folowed by prying with a screwdriver and deep regret. then a nice cuppa.

 

[Isdyldan]

Well, I did lots of jiggling and wiggling, and decided it was about to break, so I took it up to SS Motors (Chertsey) for some direction. They were very helpful, and yes AP, you are correct. The lower points should just pull out - but these don't! SS thinks it must be jammed inside somehow, so I am preparing for open-dizzy-surgery and will go in from above.
I the mean time, Joe lent me a Bosch cap and rotor arm for my original distributer which I fitted earlier, but there is no improvement. I am suspecting that there is a good chance my 'new' ecu is a dud too, and would love to try it in your car OSC if the offer is still there.
Another thought - do you think the ecu pin-out could be different for the two different types of distributer? It could be that the distributer lower points and ecu need to go together. I will research and report back!

 

[Isdyldan]

I just thought I'd post a quick up date - although things have gone backwards slightly.
I managed to lever out the lower points from above - there were two little plastic bits on either side which had jammed and I can't see that they are needed. They are not present on my original lower points set. I fitted my lower points, installed the distributer and connected the loom. I cranked the engine and there was no ignition at all. I checked the points, and they were opening and closing fine, but noticed that they were earthed at both sides. I did some testing and discovered that the green/yellow wire from the ignition amplifier had become permanently earthed somehow.
Something funny is going on - I need to do more checking tomorrow.

 

[Myros]

Dylan,

I'm looking forward to the book of the film here. This is turning into one of the better
how-to's on the forum.
Keep pix of the critcal stages, if only to save yourself future grief.
Keep up the good work

 

[Isdyldan]

Ok, I refitted the ebay electronic ignition amplifier, and it fired up again, but the same as before. (fine for a second, then 3 cylinders or so). So I now have a replacement distributer, cap, rotor arm and leads, and a different ignition unit. I think I can say I have (probably) ruled out an ignition fault. So really it points to the fuel ecu again - UNLESS I have low fuel pressure. The only reason I think fuel pressure could be a suspect again is because there is no fuel running back to the tank from the return pipe - or at least there wasn't today. I have a tube running from the return and into the filler flap so I can see what's happening. I need to get one of those gauges like you have OSC. I know we tested fuel pressure when you were over, but lots has changed since then!

 

[Isdyldan]

I disconnected the fuel line to the cold start valve and plugged the end. There was plenty of fuel there! I tried to start the car but it wouldn't run at all. I poured a cap of petrol down the air inlet and the car started and ran fine on what sounded like most of the cylinders for a few seconds, and then died completely. This is making me think that the engine is only running on the cold start valve. However, when I remove the injectors and crank the engine they DO squirt. Maybe they aren't squirting enough? Could they all be blocked??

 

[Isdyldan]

Hi - I've been reading back through the previous replies to my post and I wonder if fuel pressure could be a problem still. I bought a pressure gauge, and am getting a reading of about 1.9 bar which is a bit low from what you guys are telling me. Also, I noticed from one reply from OSC that he has his set at 3 bar to make his car run properly. OSC, please could you let me know what symptoms you had when you had lower fuel pressure? My regulator bolt is weeping slightly - I wonder if I try adjusting it will it leak more? Should the bolt be wound in or out to increase the pressure please? The fuel lines are all new, as is the filter, and the pump looks pretty new too - are there any risks in using a injector cleaner in the fuel please?

 

[mtinlin]

Stating the obvious - but there is no way any leaking of fuel is acceptable. To use a term coined by Jaguar, you are in danger of a thermal event.
Good luck!

 

[Isdyldan]

Hi - thanks for the warning! I know that I should get a new regulator, but there is no way I am replacing any more components until the thing shows signs of running correctly, unless of course it is proven to be at sufficient fault!

 

[osc]

dylan sorry for the delay in getting back to you.

yes you can try your ecu in my car if you wish.

i will repost on fuel pressure since we already covered that.

i am just worried that your haphazard approach is really not going to get you anywhere and even if you get the car started, you wont get down the road before something else fails.

to be honest if you want to get it working, i would think about stripping out the injection system and cleaning, re-furbing and re-installing. your wiring and fuel lines are in a mess, that leaking FPR is dangerous (i already suggested you should get one from bosch direct since the dealer with steal you)

sorry i'm being harsh, but hope you can see the truth. you've spent 6 months and zero progress...

 

[osc]

fuel pressure

I have a 1971 450sl and have also had problems with it so i have learned a lot about the d-jetronic system.

First I can confirm there is a fuel return line and there should be a flow of fuel back to the tank. The system is based on constant fuel pressure, controlled by the regulator and the extra flows back into the tank.

From the beginning, the fuel comes via a stainer in the tank into the prefilter then into the pump, then normal inline fuel filter. This fuel line appears in your engine bay and is the one that is towards the front of the car.

The fuel directly feeds both fuel rails (and the cold start device) then the output from the rails goes into the fuel pressure regulator (FPR; 2 input lines, 1 output) then into the fuel damper and finally into the return line. You need to connect a pressure gauge anywhere before the FPR to check that you have about 28-32 psi which is about 2 bar. Note that i've had to increase my pressure to about 3 bar to get it running right (i will put up a post about this soon). My FPR also started to leak from the screw when i adjusted it so you will need to get a new one do to bosch direct, merc charge a fortune)

I am sure I can help you fix this so get in touch and I can talk you through a diagnosis, then you can post up the answer to help any others with the similar issues.

If anyone knows about the intimate details of d-jetronic and fine tuning the system then please get in touch.

please see above.

 

[Isdyldan]

Hi - I looked up 'Haphazard' in the dictionary, and I feel this is a little unfair!
. It said:

haphazard
Adjective
1. dependent upon or characterized by chance; "a haphazard plan of action"; "his judgment is rather hit-or-miss"
(synonym) hit-or-miss
(similar) random
2. marked by great carelessness; "a most haphazard system of record keeping"; "slapdash work"; "slipshod spelling"; "sloppy workmanship"
(synonym) slapdash, slipshod, sloppy
(similar) careless
Adverb
1. without care; in a slapdash manner; "the Prime Minister was wearing a gray suit and a white shirt with a soft collar, but his neck had become thinner and the collar stood away from it as if it had been bought haphazard"
(synonym) haphazardly
(pertainym) slapdash, slipshod, sloppy

I think that as I new very little about the system at the start I haven't been THAT bad! I've checked most things in a relatively structured way, but am on a tight budget and simple can't afford to replace everything. Most things appear to be working as they should, and I've tested continuity on all the wiring. The fuel pipes are all new and apart from the leaky regulator (which to be honest is the smallest of weeps), I can't see anything to be replaced. I am now going back over covered ground and have found that the fuel pressure is a bit low. I was just wondering why one may need to increase the pressure to 3 bar - could this help my running?
As for the zero progress, I agree that if I were doing this for a living I would be long out of business. This is a hobby, and although still not on the road, it is almost there, and I have learnt loads.

 

[osc]

ok your choice....

turn the FPR screw clockwise to rise the pressure. low fuel pressure caused mine to run a bit messy and unstable around the edges. no fundamental starting problems

 

[mtinlin]

Yes, I think a change of approach is required to put us all out of our misery! Is it time to call in the professionals? I really hope you get it sorted. If I thought I could help I'd come around as I am in Woking too.

 

[Isdyldan]

Thanks OSC, I turned it up to 2.2 bar but no improvement. I agree that 'the professionals' really is the answer at this stage, and I have got SS Motors on the case. He suspects the ECU again, and is waiting for a replacement to come available to try in the car. It seems a bit odd though that the original is a dud, and that the one I bought which I was assured came from a running car is also dud. I have also had the kind offer from OSC to test the replacement ECU in his car, but we haven't had a chance for me to go up there yet. The injectors are supposed to 'fire' in pairs - cylinders 5 & 1, 8 & 4, 6 & 3, 7 & 2. The cylinders I have running are 7, 8 and 4. The injector in 2 is dud, so this would show that 2 of the 4 pairs are not working, and so could well be related to an ECU fault. I have checked the wiring.
Sorry if this is causing anyone 'misery' - it's not meant to be, and I expect it's still flagging up useful info from time to time.

 

[Alex Crow]

dylan, did you clean the injection points when you had them out? if so, what with?

 

[Isdyldan]

Hi Alexander - no, just a visual inspection and tested them individually for continuity with a multimeter. All the injectors are firing (except the dud number 2), but I don't know if the quantity of fuel emitted or the spray pattern is correct as I don't know what it should look like. This is why in a recent post I was wondering if some of the injector could be partially blocked. The engine had been sat around for quite a while before I got it.

 

[Isdyldan]

Ok, here's a strange one. Earlier today I had 3 firing cylinders - numbers 4, 7 and 8. I decided to swap the injectors from cylinders 1 and 4, which I did and now number 1 is firing - but so still is number 4!! Really odd. I have gained a cylinder
I have been trying to find some replacement injectors but they seem few & far between, and also quite pricey. Does anyone know if the injectors are shared with any other vehicles please? I have a set from a later S class which I picked up, but although the plug connectors look the same, they certainly won't fit.

 

[meanie]

I'm not going to read 24 pages (!!!) so going on recent/last post here's couple of thoughts.
It's been a long time, but as I recall the ECU sends 12v signal to the injector to operate it (double check by removing all injector plugs & the ECU plug - if I'm correct one terminal on each injector plug will have good continuity to earth. They should also be equal). Assuming that you have a good earth, check the continuity between each Injector & the ECU - should be a matter of m/ohms. If possible check the pulse of each injector - 10/20 milliseconds roughly.
Gaining a cylinder today leads me to think that you may have a harness issue.
Maybe OSC might allow you to take some resistance & voltage measurements from his system.
A short in the loom may explain the ECU issues, if that were the case.
Forgive me if you've already gone through these thoughts - 24 (!!!) pages is too much for me right now!

 

[Isdyldan]

Hi Meanie - thanks - I'll check through and see if there's anything I've not measured. I have double checked the earth (brown) wires on each injector, and also the resistance to earth of the coloured wires to the ECU, which gives about 3 ohms on all with the ECU connected. I've also checked the continuity between the 'linked' injector live wires and all ok. So I need to work out how to test the voltage and pulse with the engine running.
I am also going down the replace injector route and have been offered a set of 8 yellow injectors for a reasonable price. The yellow ones are for a 350 engine apparently, so this may lead to lean running and damage to valves according to an article I read. I can get the blue ones for about £30 each, but am reluctant to throw more money at the problem without evidence it will fix it.