2.0 190E backfired and now doesn't start...suspect fuel distributor

[hiswitsend]

Hi..this is a bit long winded sorry,

have a '92 190E running on LPG. Was coming up to a roundabout and just as I stopped I revved the car a little bit as the throttle return spring had snapped.

It started to rev then made, for want of a better expression, a noise like; 'doof' (I suspect a backfire) and the engine stopped and refused to start again.

AA guy thought it was the fuel pump as he slackened one of the feeds to the injectors and there was no fuel.

Get it relayed home and did some reading and investigation on the fuel system. When the ignition is switched on the fuel pump can be heard charging and stopping and slacking the feed to the distributor a little does show petrol seeping along the pipes.

If I manually operate the air flow plate by pushing it down a few times I can get the car to start, but it cannot maintain it.

I initally thought that the plate was a little stiffer than normal to push down, but that could be nonsense.

What should I be checking now? Had heard that the distributor may be vacuum assisted via the warm start relay(?) but only the pressure regulator appears to have a vacuum pipe of some description attached.

Could something have been dislodges or damaged in the backfire. It has done it before a couple of times, but that was down to worn distributor and rotor arm, nothing else was damaged.

Meant to bring a DVM home with me, but forgot

Hope someone can help before I start dismantling stuff.

Thanks in advance

Dave

 

[jibcl500]

Your LPG system is in need of a tune up, whats happened is the engine backfired up through the induction system, my guess is the backfire has destroyed the air flow meter, common fault on single point LPG systems.

Did you fit it yourself?????? your need a new AFM!!! and if you dont get the LPG serviced you will destroy another AFM very soon.

jib

 

[hiswitsend]

Your LPG system is in need of a tune up, whats happened is the engine backfired up through the induction system, my guess is the backfire has destroyed the air flow meter, common fault on single point LPG systems.

Did you fit it yourself?????? your need a new AFM!!! and if you dont get the LPG serviced you will destroy another AFM very soon.

jib

Fitted professionally 4 years and 80,000 miles ago. Has never missed a beat, other than down to the dizzy and rotor.

Is there a way to check the AFM?

 

[jibcl500]

is the AFM a flapper type??? if so push finger in and move the flapped if its jamming in the closed postion its kanckered.
jib

 

[hiswitsend]

Its not the usual AFM, maybe as its mostly a mechanical system...well I say that based on the Range Rover I had. Its described here: http://www.auto-solve.com/mech_inj.htm#MFI08

The sensor plate releases fuel as well which is does when the plate is moved manually and it can rev, but then fuel that was released manually is ued up it stops

 

[star]

check all the hoses on the inlet tract, beolw metering head,underside of manifold. the pop back might have blown one out so making it have a weak mixture

 

[redmansioner]

You need a new AFM and the LPG system should have to be checked and fix by a professional mechanic if you do not take action on it it may affect the other parts like the Mercedes Benz oxygen sensor which is likely to cost you even more expenses if the whole thing is left unrepaired.I hope i could help.

 

[hiswitsend]

Its FIXED

Had read on the forum that there was a pip that had a habit of coming out, but couldn;t find it

SO was reluctantly getting ready to strip it all down and decided to have one last chance and was able to get my hand right underneath the manifold and felt a short, thick, pipe thing that seemed loose. Took it out, it looked ok, put it back under and managed to locate it and voila the car now starts!!

Just glad I found it, didn't think there wer any pipes that far under.

Cheers

Dave

 

[beemerjay]

Its FIXED
Had read on the forum that there was a pip that had a habit of coming out, but couldn;t find it

Glad you found your pip

 

[hiswitsend]

Glad you found your pip

hehe, yup, think I'll go for seedless next time

 

[television]

This was all beyond me but I enjoyed reading it, and there is a happy ending

 

[Thegemmesabogie]

Sorry I was late reading this post. What blew off and you found was undoubtedly the long U shaped pipe (107) linking the intake plenum to the idle valve (113). It used to do it regularly on my 230 TE LPG. What you need to watch for is the nylon stub (29) that links the pipe to the manifold end. It can blow off and be lost if the car is moving. I drilled the flange on mine and retained it with a short length of fishing line. Manifold backfires are one of the only drawbacks on LPG. One way to help avoid them is to close the plug gap by a couple of thou and change the dizzy cap and leads on a fairly regular basis. Dont be tempted into securing the U pipe; any future backfire may then cause real damage. Probably to the metering flap.

http://www.detali.ru/cat/oem_mb2.as...+++717.412&CT=M&cat=504&SID=09&SGR=060&SGN=02

 

[hiswitsend]

Sorry I was late reading this post. What blew off and you found was undoubtedly the long U shaped pipe (107) linking the intake plenum to the idle valve (113). It used to do it regularly on my 230 TE LPG. What you need to watch for is the nylon stub (29) that links the pipe to the manifold end. It can blow off and be lost if the car is moving. I drilled the flange on mine and retained it with a short length of fishing line. Manifold backfires are one of the only drawbacks on LPG. One way to help avoid them is to close the plug gap by a couple of thou and change the dizzy cap and leads on a fairly regular basis. Dont be tempted into securing the U pipe; any future backfire may then cause real damage. Probably to the metering flap.

http://www.detali.ru/cat/oem_mb2.as...+++717.412&CT=M&cat=504&SID=09&SGR=060&SGN=02

That's the very pipe! Strangely missing from the Haynes manual pictures :? ..well not that I could see.

Think the nylon stub was still in it as the pipe did fit back on, aslo it happened while stationary and there was nothing on the road.

The LPG system as some sort of timing retardation that's meant to help prevent backfire, but reckon it was the fact that it was almost stalling and I tried to catch it that caused this, but have replaced the leads and will close up the gap on the plugs as well though.

Cheers

Dave
Dave