P38 2.5 Plug Relay Faulty?

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amongstit

New Member
Posts
44
Location
Rutland
Recently had a problem with my glow plugs with 2 weeks of difficult starting,after fitting 6 new plugs (Britpart) my starting problem has now changed.
When I start from cold it doesn't fire at all no matter how long I turn the engine,it's like the plug relay is asleep because if I reset the ignition and wait for the glow plug light to go out for a second attempt it starts instantly.
As I said even if the first starting attempt is a quick two turns of the engine or just the extinguishing of the plug light it never fails to start on the second attempt so I think it's not fuel related,maybe my plug relay is now faulty due to the 2 weeks of strenuous starting? thanks.

Also probably worth mentioning I recently had my alarm turned off and put into 'Dubai mode' and since had a flat battery.
 
How long is the glow lamp on for? Should be seven or eight seconds. You should wait for it to go out before starting car. Your problem maybe that if it is not powering the plugs for long enough, they don't get hot enough on first application, heating from cold, but do on second application heating from warm. So yes you may have a failing plug relay if it does not stay on for seven seconds or more. Or if it does stay on you may have bad connections on it, causing a voltage drop at plugs, check for 12 volts at plug terminal with glow lamp on.
 
You seem to discount a fuel problem....

When you turn the ignition on the In-Tank Pump (ITP) runs for a few seconds to repressurise the fuel lines....then when cranking the ITP runs again to supply fuel pressure to the Fuel Injection Pump (FIP).

If during your first start cycle their is air in the fuel lines (due to leaky leak-off pipes or similar issues) all that is ahppening is the pump is trying to expell the air....when you try the start cycle once again, their is little to no air in the fuel lines and as such starting is easier (plus the benefit of double heated glow plugs)....

Have you checked the leak-off pipes for splits or leaks?...might be something else to look at, but far be it from me to tread on the toes of the Wammer who is, without doubt, 'da man' when it comes to such things....so heed his advice as I could be way off mark....
 
Saint.V8 said:
You seem to discount a fuel problem....

When you turn the ignition on the In-Tank Pump (ITP) runs for a few seconds to repressurise the fuel lines....then when cranking the ITP runs again to supply fuel pressure to the Fuel Injection Pump (FIP).

If during your first start cycle their is air in the fuel lines (due to leaky leak-off pipes or similar issues) all that is ahppening is the pump is trying to expell the air....when you try the start cycle once again, their is little to no air in the fuel lines and as such starting is easier (plus the benefit of double heated glow plugs)....

Have you checked the leak-off pipes for splits or leaks?...might be something else to look at, but far be it from me to tread on the toes of the Wammer who is, without doubt, 'da man' when it comes to such things....so heed his advice as I could be way off mark....
Click to expand...


If he has air in the FIP cracking an injector will clear it. But it could be fuel related if he has leaky spill pipes or filter O rings. But if no air in clear pipe at any time, more likely to be as i said earlier.
 
I've got similar starting issues with my R reg 2.5 DSE.
Bought the car back in the summer and it was an excellent cold and warm starter, no problem. The car came with the glow plug timer/relay 'bodge box' fitted just behind the ECU, which as I understand it simply gives heat on a warm start as well as a cold start (right?).

Now I'm getting very poor (sometimes NO) cold start. I think an important aspect of this is that I'm using the vehicle very infrequently at present (eg only starting it every few weeks).

My first inclination was to suspect the glow plugs relay, as a warm start a few hours after running the car resulted in a fine start. However I've got 12v going to the glow plugs, and it seems unlikely that the plugs have failed suddenly to make such a dramatic difference. Much more likely (from reading these excellent pages) is air in the diesel feed pipe, which I think gets worse if the car left for several days. I can definitely see air in the clear filter-to-injection pump section of the pipe.

So, renewed the leak off pipes (long one from the FIP to the first injector very cracked, giving me hope!). Pipe cost me £3/metre.

A good long crank and it nearly started, but not quite, trying again this morning after battery recharge, still air in that clear pipe. Hoping that it's been introduced by the leak off pipes and once started will clear and not get more. Logical??

Maybe I'm going to need to give the FIP a hand by 'cracking off an injector; to bleed that air? Wammers can you say a little more about how to do that please?

If it matters the car also came with the 'PSI Powerbox' tuning thing. did 2k miles over the summer, getting just over 30MPG, which is about 2 more per mile than the '53 Disco 2 I had previously!!
 
My glow plug light stays on for 7 seconds as it always has and this morning it wouldn't start until the third attempt so the problem is getting worse.
I replaced the leak off pipes some months ago and there's no air in my feed pipe.
I guess now I need to test the voltage going to the plugs so I'll go buy a multimeter today,I'm guessing I'll be setting it to 12v,making a positive contact with the back of a plug while somebody turns on the glow light?
 
amongstit said:
My glow plug light stays on for 7 seconds as it always has and this morning it wouldn't start until the third attempt so the problem is getting worse.
I replaced the leak off pipes some months ago and there's no air in my feed pipe.
I guess now I need to test the voltage going to the plugs so I'll go buy a multimeter today,I'm guessing I'll be setting it to 12v,making a positive contact with the back of a plug while somebody turns on the glow light?[/quote]

Correct. I would hazard a guess that your ****part glowplugs are NBG. You are not the first to fit new glowplugs that do not work:eek:
Click to expand...
 
amongstit: I was able to stick my multimeter +ive on the connector on the glowplug and it let me know there was nothing wrong my relay.

With reference to my posting of earlier today and thinking it was more to do with air in the feed, rather than a glow plug issue, I think I was probably barking up wrong tree. Lots of cranking and spluttering but no joy this morning, after doing the bleed off pipes yesterday. Time to test glow plugs.Wasn't convinced as they looked new, and were (better?) NKG ones. (I did take the manifold off btw, following advice on this forum). Tested the plugs using my jump leads (carefully!). Should have guessed only one was working, it was the one that came out dry looking, the non-working ones were all oily.

Off to buy a deep 12mm 3/8 drive socket now, which would have made extraction much easier!

Hoping this will sort my starting issue, will advise.
 
revmarkp said:
amongstit: I was able to stick my multimeter +ive on the connector on the glowplug and it let me know there was nothing wrong my relay.

With reference to my posting of earlier today and thinking it was more to do with air in the feed, rather than a glow plug issue, I think I was probably barking up wrong tree. Lots of cranking and spluttering but no joy this morning, after doing the bleed off pipes yesterday. Time to test glow plugs.Wasn't convinced as they looked new, and were (better?) NKG ones. (I did take the manifold off btw, following advice on this forum). Tested the plugs using my jump leads (carefully!). Should have guessed only one was working, it was the one that came out dry looking, the non-working ones were all oily.

Off to buy a deep 12mm 3/8 drive socket now, which would have made extraction much easier!

Hoping this will sort my starting issue, will advise.
Click to expand...

Well if it doesn't you have a big problem but i think it will. Proper way to bleed clear pipe is to open slightly the banjo on the pump and get someone to switch ignition on nip when air is out. Cracking injectors is done with engine running, just open each injector in turn a little to get any air out of FIP. Then when you get a good flow of diesel nip it back up. you may need a split obstruction spanner or crows foot for this.
 
Tested the voltage from the relay to the plugs and I'm getting 10.5 volts ,my battery is reading 12.5v. Is 10.5 volts low enough to cause my starting problem?
 
amongstit said:
Tested the voltage from the relay to the plugs and I'm getting 10.5 volts ,my battery is reading 12.5v. Is 10.5 volts low enough to cause my starting problem?
Click to expand...


Battery voltage is marginal, voltage at plugs is enough to heat the plugs allowing for the volt drop in the cables. You could check for bad earths to the engine block. I still reckon it's your glowplugs:)
 
amongstit said:
Tested the voltage from the relay to the plugs and I'm getting 10.5 volts ,my battery is reading 12.5v. Is 10.5 volts low enough to cause my starting problem?
Click to expand...

I would say that is your problem, you should have more than that with only glows activated. Relay maybe suspect or earths as Data says.
 
to update on my glowplug failure problem, a new set (bosch ones from fleabay) DID solve my starting problem, just as wammers predicted.

On the bench with the multimeter the duff plugs (5 of the 6) either had full or substantial resitance when testing for continuity. The good plug had no resistance. so I guess that test could be done without removing the plug, if the power wire was removed; simply test for continuty between the +ive connection and chassis, to see of the plug is good.

Now would my new faultmate have told me that I wonder?!!
 
revmarkp said:
to update on my glowplug failure problem, a new set (bosch ones from fleabay) DID solve my starting problem, just as wammers predicted.

On the bench with the multimeter the duff plugs (5 of the 6) either had full or substantial resitance when testing for continuity. The good plug had no resistance. so I guess that test could be done without removing the plug, if the power wire was removed; simply test for continuty between the +ive connection and chassis, to see of the plug is good.

Now would my new faultmate have told me that I wonder?!!
Click to expand...

Yes it can. Faultmate would not report duff plugs.
 
Mine went from a good starter to reluctant a few weeks back. It was a glow plug problem. I found that I could change number 2, 5 and 6 without removing the manifold. One was OK reading a few Ohms matching the new ones, one of the others was open circuit and obviously duff but the second was showing a higher resistance. I changed them both and it's now back to being a good starter. I'll get the others when the manifold has to come off for some other reason. The replacements from the local shop were Lucas brand and seem OK (so far). I have a hot start box fitted so they do have a harder life than envisaged.

I found my long 1/2" AF socket worked well with a turn of cardboard around the new plug to hold it with the thread projecting. Similar turn of cardboard to hold the 8mm terminal nut - getting number 2 back on was a struggle with a number of attempts and dropped nuts!
 
Datatek said:
Battery voltage is marginal, voltage at plugs is enough to heat the plugs allowing for the volt drop in the cables. You could check for bad earths to the engine block. I still reckon it's your glowplugs:)
Click to expand...

Bang on the money again Data,cheers. I changed the Britpart plugs for a set of Delphi and on the first starting attempt it fired up instantly :D
I've been told the plugs don't get hot enough,even enough,quick enough.
When I told this to the seller he said he'd sold thousands of these plugs with no problems and that Britpart's bad reputation is out of date and no longer deserved, I find that hard to believe though I do wonder why some P38's have no 'initial' problems with cheaper plugs, my guess is beefier batteries or the difference between the Lucas and Bosch electrics on the earlier and later models.
 
amongstit said:
Bang on the money again Data,cheers. I changed the Britpart plugs for a set of Delphi and on the first starting attempt it fired up instantly :D
I've been told the plugs don't get hot enough,even enough,quick enough.
When I told this to the seller he said he'd sold thousands of these plugs with no problems and that Britpart's bad reputation is out of date and no longer deserved, I find that hard to believe though I do wonder why some P38's have no 'initial' problems with cheaper plugs, my guess is beefier batteries or the difference between the Lucas and Bosch electrics on the earlier and later models.
Click to expand...

Some of the cheapo glowplugs degrade very quickly:eek:
 
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