Hi all, for the past few days I've been trying to sort out why my car is getting to be a pig to start from cold. It never fails to start but runs as if on 3 cylinders to begin with accompanied with a cloud of blue smoke. After less than a minute it settles down to normal and pulls like a steam train again.
So far I've replace the rubber fuel hoses and the leak off pipes, the glow plugs, stripped and cleaned the injectors, replaced the primer head on the fuel filter with a spare, and replaced the air filter. There is no preheater fitted.
Other than this initial starting problem the car runs great so any ideas what's wrong ?

Cheers, Colin.P (no Peter.N, I haven'y fiddled with the mixture screw - yet )

Hi Colin

You do not mention checking the glow plug relay and its wiring. The relay and wiring take a heavy current and can deteriate badly with age. The glowplug light in the car is just that, an indicator light and not a monitor that all is well with glowplug operation.

John

Hi..

The light on the dash WILL ONLY light WHEN the plugs are heating! Thats what the black relay control box actually does... I know this from a recent Xantia DERV problem.. the heater light was flashing on briefly and the car would'nt start, however, another day the light stayed on for its duration and it did start... eventually, it failled completely and would NOT light up at all.. I traced it down to a feed signal fault to the black box, not activating it.. I replaced it all with a manual push button heat system, and put the light onto the out put side for the owner to tell the heaters were heating..

Anyway... back to Colins problem, I found this on a DERV I had in.. Has she got Bosch Mechanical injection Colin??

IF SO you WILL need to advance the pump on its dowls to help cure the problem... DONT ASK WHY... but I've had this problem with a few Bosch equipe cars, Xantia and XM, and discovered if I undid the 3 bolts at the pully end, and the one below the pipe out put end, and swiveled the top end of the pump TO the engine, advancing the timing, it cured the problem... I get the feeling the cold start advance on the Bosch pumps get tired or sticky with age, or milage...

Ill probably get shouted at for incorrect advice, but its how I solved mine...


Good luck...

Rgds
PAul

Hi Paul

My experience with one of the 2.5's in regular use is that the light can still operate independant of what is happening to the glow plugs. I think we have had the discussion about dash lights before. All the dash indicating lights have their own power feed so they just need a voltage or earth signal to be brought on. An intermittant wiring fault can set them going just as easily as the correct signal. That is why critical indications such as ABS and Airbags have blinking startup sequences.

John

I also have a 2.5 that became progressively more difficult to start in the mornings last winter. I diagnosed a shot glow plug and for several reasons kept puting off the job until things got so bad that I missed golf one morning because the car barely refused to start. Nothing like missing golf for galvanised me into action and I replaced all the glow plugs. Only one of them was working, but as John also reported the dash light behaved normally as before the problem arose.
Before bolting the relay in position I started the car to ensure all ok -started first turn . Bolted relay on went to start car - would not fire up, no power to plugs.
On mine there is a small plug with 4 or 5 fine wires moulded into it that connects to the relay box. It is secured by the familiar wire clip. I removed, cleaned and vaselined the contacts and problem solved. I assume the fine wires fed the relay control current , the temp. sensor signal and dash light.

Noz mentioned a dual relay on his 2.5 each feeding 2 plugs, mine is a single feeding all 4 plugs.

Robert

It is possible to open the relay and see if it is working, it is glued together,but a knife inserted in the joint and some patience and perseverance gets the cover off, it can be clipped back on after this. You can then see whether the points are working as they should together with any pitting etc. corrosion on the feed to the plugs kills them as well.
cheers,
Dod

Hi Colin

If you have access to a meter, connect it between any glow plug top connection and earth and swith to the glow plug position, you should get a reading of about 10-11 volts, if all the glow plugs are working, all the while the relay is closed, the light will very often go off before the relay drops out, the extra time is to prevent it smoking while still cold. No volts - no work. You can always try connecting a length of wire direct from the battery + to the plugs for about 10-15 seconds, fairly thick wire though as the plugs take about 60 amps between them.

Paul

Strange you should mention the pump timing in relation to starting. When I bought the black car it sounded like an early DI transit at about 2000 rpm, apart from the noise I reckoned that it was likely to suffer damage being that much advanced, so I retarded it by about 1/16", it no sounds much better and drives fine, as I expected though it became more difficult to start and at tickover speed sounds to quiet, I reckon the the the timing advance is overdoing it, whether its been fiddled with or its just wear and tear I dont know, I was going to take it to a pump specialist but it starts OK if you dont try until you hear the relay drop out so I havn't bothered.

Peter

For the relatively small price of a set of new glow plugs I think it is worthwhile changing them on a regular basis in the same way as you would with spark plugs.
The main problem is that they are a pig to get at and I always end up dropping one or more of the tiny terminal nuts in the process!

Ken

As noted, the fellow member HAS changed glow plugs... So other sugestions.. as per my post, Pump Timing is playing up.....

I insist!

Paul

Hello everyone, many thanks for all your replies I've just been out and tried 3 different relays while measuring the voltage transfered by each to the plugs as Peter.N said to try. Each gives 9.8 volts to begin with gradually increasing to around 10.5 volts before the relay trips out. Is this really enough ? the supply to the relay measures 12.2 volts with the ignition off but measures exactly the same as at the glowplug end when the ignition is switched on.
I know the glowplugs work as they should as i tried them across the battery before installation.

DOD, I have opened up all 3 of my relays and all of them have some pitting on one contact with the accompanying build up of material on the other. On all 3 I've filed and cleaned up the contacts as much as possible but they all perform exactly the same so I don't think it's this that is to blame but thanks anyway

Paul, I do indeed have a Bosch pump fitted, I put it on when my original Lucas EPIC system packed up. Do you know, I spent ages getting the static timing set just right using a dial guage... It'll really tick me off if I have to advance it when the pump was first fitted, the car started better than it ever had in my ownership, will it need to be retarded again when the weather gets better ? how much would you suggest I rotate the pump ?

Best wishes Colin.P

Hi Colin, just to clarify the basic electrics, 1/ the glow plugs are conected in parallel and therefore considered connected to a common supply rail.2/if you measure ANY voltage at all at this supply rail with ignition on(at any of the glowplugs connecting nut) then the glowplug relay/timer IS operating.3/ each glow plug is approx 1 Ohm in value therefore draws 12 Amps from a 12Vdc source, therefore total current draw is approx 50 Amps,4/this level of current draw can pull the battery voltage below 10Vdc - particularly if the battery has had some years of sevice - (any more than this and heating effect drops off exponentially)and correspondingly the total current will fall off.None of this indicates a fault with supply or control unless the battery votage falls below approx 10 V.Try switching your headlights on during glowplug operation, if the measured voltage plummets it's time to change the battery.The glowplugs can only be adequately tested by measuring the current drawn by each.This means disconnecting all the plugs to measure total current draw or individually by connecting a suitably rated ammeter in series with each plug - as you effectively did by connecting each to a battery in turn.Depending on model/engine the timer/relay remains energised after starter engagement but at REDUCED voltage (low heat mode) until a coolant temp level of -i think,will try to dig out the value - 40 deg or a time out mode of - again can't remember - 4 minutes i think.Yes, the glowplugs remain energised with engine running,EU TO BLAME, emission controls.The instrument panel light times out after 10 to 15 secs and is not an indication the timer/relay/glowplugs have operated.Go with Paul on this one, you've done the electrickery bit!

Hi Colin

As Robert says that voltage sounds about right, as the plugs get warm their resistance increases, hence the voltage rise. The sort of voltage your are getting would indicate a fully working glow plug system.

Peter.

Cheers Robert for an explanation that even I can understand if you ever need anything making on a cnc I'm your man but electrics are a bit beyond me

Looks like I'm going to try the pump timing trick after all

Best wishes Colin.P

Does priming the fuel system while trying to start the engine improve matters. If it does, then your problem is probably the fuel heater. It is a rubbish casting and goes porous after about 50,000 miles. The fuel pump suction prefers to draw air through the casting than lift the fuel up from the tank. I have changed a fuel heater once at a cost of £50, and later performed a fix on the second one. If you are still in doubt if the fuel heater is the problem, then modify the plumbing to by-pass the heater and drive it around a bit. Let me know if you want to know what the inexpensive fix is.