Rough start

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Phanc60844

Member
Posts
58
Location
Stoke on trent
Hi all,
Ive got an issue on starting, used to be on the button with no hint of smoke, then it would take 3 trys to start, run rough for about 5 seconds then normal. During this period it would blow greyish smoke. Changed the fuel filter and air bleed valve, also fitted the LP return pipe non return valve which wasnt there before. Now after several purge attempts, starts first time but is still rough and smokey for 5 seconds.
Any ideas, injector seals, fuel pump? The fuel pump is only 5 months old but was a cheap copy, the fpr block was changed due to leaks a month ago for a genuine unit. The car runs fine and doesnt smoke or hesitate , returns 22mpg on a 100 mile trip pulling a 2.5 tonne trailler, no engine oil loss. Engine was rebuilt 1250 miles ago, bores honed, new rings, crank, oil pump etc.,
Any ideas?
Thanks
Paul
 
Glow plugs stay on for a while, after the light goes out, to assist detonation of the fuel until the engine reaches a good working temperature. Unless you are operating in a hot country, the TD5 definitely needs a good set of plugs.

 
I measured once at - 8*C from cold start and they stayed on a bit more than 3 minutes with engine running, it's called post-heat operation and it works always when the ECT is below 20*C from start(that's not mentioned in the manual, i made experiments)
 

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tilly2 said:
Disconnect them, and try again....
Click to expand...
Why would I disconnect them? its already running rough on cold start
tilly2 said:
Glow plugs stay on for a while, after the light goes out, to assist
detonation of the fuel until the engine reaches a good working temperature. Unless you are operating in a hot country, the TD5 definitely needs a good set of plugs.

Click to expand...

Ok, when i got home, just as an experiment, i swapped the glow plug relay and tried to start. All issues had gone, however it has warmed up a little in the padt couple of days. Should really have checked the voltage at the plugs to make sure but couldn't be arsed to remove the beautification cover. Pulled the relay apart and there were splash marks on it. Tested at 0.1ohm with the meter but that means nothing as its not under load. Will try another start when the cold weather returns
 
If it made it worse, then you know they are working... if it starts the same way, then thats not the issue.

My engine cover only gets fitted at MOT time, otherwise its a pain in the arse to keep removing it to see what the fook has gone wrong now...
 
Last edited:
Same issue here, I've tried it with/without glow plugs - no difference. The issue starts at 5°C....The glow plugs are 1 year old....
 
So did you measure if voltage gets to the plugs ? if yes measure theyr's resistance across the terminal and head, it should be close to 0.9 Ohm
 
Im going to replace mine as a part of ongoing maintenance. Beru or Bosch are my choice. Not cheapo, four for a tenner crappy ones...
 
Well now the cold weather is back, so is my rough start issue. Ive checked the resistance of each plug, 0.5ohm. I get 11.5v on each plug so ive got a 1v drop from the battery. If i plug in Hawkeye and force the glowplug relay in for about twice the normal time it runs fine. The coolant sensor and ambient air both read 2degc , weather channel said it was about 1degc so close enough. Is there anything else that affects the glowpug on time?
 
Mario110 said:
Same issue here, I've tried it with/without glow plugs - no difference. The issue starts at 5°C....The glow plugs are 1 year old....
Click to expand...
Those plugs are ''tired'' , should have 0.9-0.8 ohm nothing less. It has two coils within and it can have winding short in the regulating side even if they say it can't so the resistance drops and the whole function is mixed up. These plugs are more complex than they appear, i selected the relevant info, see attachment
 

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sierrafery said:
Those plugs are ''tired'' , should have 0.9-0.8 ohm nothing less. It has two coils within and it can have winding short in the regulating side even if they say it can't so the resistance drops
and the whole function is mixed up. These plugs are more complex than they appear, i selected the relevant info, see attachment
Click to expand...

Im not so sure, they have done 1500miles, were a good make, the £14 pound ones not your 4 for a tenner. The resistance is exactly the same for each, if there was one or two that were slightly different then id agree. Anyway, running at 0.5ohm would mean that they would run twice as hot as one at 0.8/0.9.As it works when i force the relay on for longer, Im erring towards volt drop being the issue so a new relay is on its way
 
Phanc60844 said:
Im not so sure, they have done 1500miles, were a good make, the £14 pound ones not your 4 for a tenner. The resistance is exactly the same for each, if there was one or two that were slightly different then id agree. Anyway, running at 0.5ohm would mean that they would run twice as hot as one at 0.8/0.9.As it works when i force the relay on for longer, Im erring towards volt drop being the issue so a new relay is on its way
Click to expand...
Ok, what do i know ? if they had 0.5 ohm from the beginning they are not the proper ones and that's why your relay gets hot. Lower resistance doesnt meant that they get hotter, if they were hotter you shouldnt have kept them more under power. The stores are selling all kind of them apparently compatible but there are types with 0.5 ohm from factory which are not mentioned as "after glow capable" and others clearely described and those have 0.9 ohm and that's how the genuine LR ones are, i measured them not once, also they are all designed to work at 11V , this type is the good one https://www.autodoc.co.uk/ngk/7155984 , and this one is not https://www.autodoc.co.uk/denso/1665194 cos it burns out the relay
 
A 0.9ohm glow plug will draw around 13 amps, where a 0.5ohm plug will draw twice that. So, four good plugs will draw just over 50amps, and four low resistance ones will draw around 100amps. On a car that isnt running, thats drawing that current straight from the battery, whilst the starter is cranking. Thats quite a load for the battery to take if its not in tip top condition. Might be worth sticking a volt meter across the battery whilst its cranking, to see if the voltage is sustained enough for the engine management to operate correctly.
 
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