W124 M104 idle issues

[MB-tex]

Hi all

my 1996 e280 is giving me issues and is currently in the shop. I don't like it when a car has to stay in overnight!

Basically car has been failing to start then starting first time later in the day. Also coming off a roundabout it has felt like it lost power until car was level again. The car finally would not start so I towed it into the shop this morning.

Fuel filter and 2nd fuel pump changed and car started. But would not idle so mechanic was investigating idle valve at end of day...

Bad throttle wiring, loom issues? Vacuum line disconnected somewhere? Any clues to follow up gladly received as my mechanic seemed to have drawn a blank by the end of the day - and I need the car!

Thanks all

 

[bolide]

Good luck inspecting the idle valve on an E280. It doesn't have one

Everything is managed by the ECU so all sensors & etc are suspect. Could be MAF, crank sensor, TB, loom, etc, etc. Not much in the way of diagnostics on these cars apart from blink codes. What fault codes did the code reader throw up?

Nick Froome

 

[MB-tex]

Thanks Nick

Don't know codes that were read. Car is in AJ Robertson but Alan is away. I'm sure his colleagues are up to the job in his absence but I do miss his guru-esque knowledge when I take my old merc in there. Hopefully they can get to the bottom of it tomorrow and it won't be too expensive. Keep your fingers crossed that its not something terminal. I suspect it is degrading wiring somewhere. I have got away with it so far (250k miles on original loom) so probably time for some issues!

Tom

 

[brigadier]

Loom would be the first thing to check. It MUST be perished if it's indeed original.

 

[bolide]

MB-Tex, drop me an email or give me a call. I don't do PMs

Nick Froome

 

[MB-tex]

Hi All

Car still in shop and mechanic is not sure what to do. He is still convinced it is fuel pressure problems. The loom is good as far as I can see. All the wires visible show no sign of degrading at all. It is the original loom (1995). He has cleaned the throttle body and that wire looked ok too. Car starts and runs fine under power but will not idle. Gave a big pop from exhaust when it died. He thinks the fuel pressure regulator is next to check. These are 73+Vat (part number 000 087 15 89) from merc but only from Germany, delivered by Tuesday! This part on the car is dated 1995 too. How long do these FPRs last? Is it worth fitting a used one and what are the symptoms of a failed unit?

Any advice gratefully received.

Thanks

 

[grober]

Hi All

Car still in shop and mechanic is not sure what to do. He is still convinced it is fuel pressure problems. The loom is good as far as I can see. All the wires visible show no sign of degrading at all. It is the original loom (1995). He has cleaned the throttle body and that wire looked ok too. Car starts and runs fine under power but will not idle. Gave a big pop from exhaust when it died. He thinks the fuel pressure regulator is next to check. These are 73+Vat (part number 000 087 15 89) from merc but only from Germany, delivered by Tuesday! This part on the car is dated 1995 too. How long do these FPRs last? Is it worth fitting a used one and what are the symptoms of a failed unit?

Any advice gratefully received.
Thanks

http://www.cardiagnostics.be/-now/Educational_sites_bestanden/BOSCH L-Jetronic Injection Manual.pdf page
pages 15/16 the unit is pretty simply just a spring loaded diaphragm the diaphram is an elastomer which is what is likely to fail/leak A new one is your best bet.

 

[grober]

Puzzled by that part no as A000 078 15 89 is for the M111 4 cylinder engine

EPC didn't recognise A 000 087 15 89???

Might explain the lack of idle?

 

[MB-tex]

Thanks Grober. Yes that's what it looks like in situ - a simple diaphragm device. That part number is correct - I attach a picture. Makes sense that a failed unit would cause idle issues I guess. This regulator has been on the car since I had it and probably since it was made! Anybody had one fail before and what were the symptoms?

Found some info here on the FPR:
HOW-TO: Replacing M119 / M104 fuel pressure regulator

 

[MB-tex]

Mechanic has pressure tested the FPR and it seems like it is pressure-less so that is my direction of travel.

Ordered up a new regulator from ECP. Bosch part number 0 280 160 587. Was on at £118 but after some haggling got it for £89. Will fit it on Monday and the car will work perfectly and won't give me any more problems for several years to come.

 

[grober]

Certainly that updated part no A 000 078 18 89 is the one I found for the 2.8 M104.94* engine. Might be worth going for the equivalent bosch part 0 280 160 587 @ £38
https://www.buycarparts.co.uk/bosch/677349
many other suppliers.

sorry I see you have gone down that route already - hope it solves the problem

 

[bolide]

What's the fuel pressure coming out of the fuel pump?

Nick Froome

 

[BlackC55]

Those fuel pressure regulators are so reliable. I have not ever changed one.

Id be looking at the fuel filter or fuel pumps firstly. But as bolide has suggested above id be checking fuel pressure. It should be just under 4 bar. The fuel pump relays are prone to fail too.

 

[MB-tex]

Thanks guys

Don't know the pressure out of fuel pump. I will call by the shop shortly and see if he has checked. New pump and filter fitted this week. Where are the fuel pump relays and any obvious symptoms of them failing?

Tom

 

[BlackC55]

There are two pumps on an estate....

 

[MB-tex]

They replaced the 2nd fuel pump (under the plastic shield). No knowledge of pressure from pump when i visited mechanics just now.

So I wait till Monday to fit the new fuel pressure regulator and hopefully I can add a 'solved' tag to this thread...

 

[MB-tex]

solved

Hi all

Car fixed and back on the road. It was the fuel pressure regulator (see attached pics) that sits at the end of the fuel rail. Maybe this also made the fuel pump overwork that caused it to fail? Bosch part number 0 280 160 587. £83 from ECP. Anyway, all well that ends well and I am glad to be back in the old girl. Have been driving a borrowed nissan micra and a borrowed alfa gtv 2.0 neither of which would tempt me away from the old barge. But driving newer cars does remind you of the fact when you get back in, that these w124s really are old barges...

On another note whilst looking into possible loom repairs I called Sileck who do motorsport auto wiring (Sileck Motorsport Wiring) and got a quote to repair the loom. They have done lots of these and charge approx £350 and £60 for throttle body rewire. Turnaround time 10 days to 2 weeks. Will get mine done one day...

Thank you all for advice

Tom