P38a Diesel Rattling Chain now difficult to start.

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jimllshiftit

jimllshiftit

Active Member
Posts
225
Location
Warwickshire
Evening all. Suppose I should have sorted this out a while ago but its never been high on the priority list.

The P38 hasn't sounded particularly smooth for the last year or so as the timing chain always sounded like it was becoming a bit rattley to me. After replacing the leak off pipes, installing a valve in the fuel line and replacing the leaky master injector it always started easily and ran well enough so I just left the chain be.

This week however its started to be troublesome to start. Not serious at the moment but its taking longer than it should before it fires up and even then it needs a fair bit of throttle before it'll catch.

After reading so many old posts about timing issues being responsible for poor starting issues, im wondering if I should investigate this rattly chain. Whats the best course of action here, lads?
 
jimllshiftit said:
Evening all. Suppose I should have sorted this out a while ago but its never been high on the priority list.

The P38 hasn't sounded particularly smooth for the last year or so as the timing chain always sounded like it was becoming a bit rattley to me. After replacing the leak off pipes, installing a valve in the fuel line and replacing the leaky master injector it always started easily and ran well enough so I just left the chain be.

This week however its started to be troublesome to start. Not serious at the moment but its taking longer than it should before it fires up and even then it needs a fair bit of throttle before it'll catch.

After reading so many old posts about timing issues being responsible for poor starting issues, im wondering if I should investigate this rattly chain. Whats the best course of action here, lads?
Click to expand...
Have you checked the glow plugs? Weather is getting colder so they are more needed. Three working if in the right cylinders is enough to start it until it gets too cold. The other thing to check is the modulation, if the timing chain really is worn, it will be way off and make starting difficult. Modulation should be 50% at idle with the engine temperature at about 95C.
 
Cheers DT. I havent checked the plugs but i replaced them with Bosch plugs about 2015 and the car only does about 4000 miles a year. Would you expect them to be questionable after such a relatively short life? That big fat fuse in the bottom of the fuse box is intact and although I made the assumption during the warmer months that the glow plug timer was OK could that be suspect? Its pretty chilly out there this morning but this time it fired up pretty well.

Without wishing show my ignorance, could you explain what "modulation" is? ive genuinely never heard that term and a quick google search shows me something about radio waves.

Maybe im just being paranoid. Theres another p38 diesel going about town near me and I took the time to listen to it idling when I saw it outside a supermarket a few weeks ago. It sounds a damn sight smoother than my one.
 
Last edited:
jimllshiftit said:
Cheers DT. I havent checked the plugs but i replaced them with Bosch plugs about 2015 and the car only does about 4000 miles a year. Would you expect them to be questionable after such a relatively short life? That big fat fuse in the bottom of the fuse box is intact and although I made the assumption during the warmer months that the glow plug timer was OK could that be suspect? Its pretty chilly out there this morning but this time it fired up pretty well.

Without wishing show my ignorance, could you explain what "modulation" is? ive genuinely never heard that term and a quick google search shows me something about radio waves.

Maybe im just being paranoid. Theres another p38 diesel going about town near me and I took the time to listen to it idling when I saw it outside a supermarket a few weeks ago. It sounds a damn sight smoother than my one.
Click to expand...
Modulation is a function of the Fuel Injection Pump timing and if you have a Nanocom you will find it in the engine ECU screens.
Put a meter on one glow plug, get someone to turn on the ignition and see what voltage you have. With a fully charged battery expect around 11 volts.
 
The diesel pump has an electronic adjustment in the top of the pump that alters the point off injection , when the pump is timed up with the chains and timing marks it is them fine tuned by turning the pump body till you get the 50% modulation figure this sets the electronic part to the right start point so the point of injection is spot on,
as the chains stretch and wear over time the modulation figure goes up and the pump goes out of timing, part of the service scheduled is to re time the pump to take up the chain slack, this involves slackening the pump mounting bolts and tapping the pump body in towards the engine probable less than 1mm to bring it back to the 50% figure.
 
jimllshiftit said:
Cheers DT. I havent checked the plugs but i replaced them with Bosch plugs about 2015 and the car only does about 4000 miles a year. Would you expect them to be questionable after such a relatively short life? That big fat fuse in the bottom of the fuse box is intact and although I made the assumption during the warmer months that the glow plug timer was OK could that be suspect? Its pretty chilly out there this morning but this time it fired up pretty well.

Without wishing show my ignorance, could you explain what "modulation" is? ive genuinely never heard that term and a quick google search shows me something about radio waves.

Maybe im just being paranoid. Theres another p38 diesel going about town near me and I took the time to listen to it idling when I saw it outside a supermarket a few weeks ago. It sounds a damn sight smoother than my one.
Click to expand...

That does sound like hot-start issue. When chains get really stretched it starts to cut out on the manual as you approach roundabouts or the engine management list flicks on on the auto.
 
Grrrrrr said:
That does sound like hot-start issue. When chains get really stretched it starts to cut out on the manual as you approach roundabouts or the engine management list flicks on on the auto.
Click to expand...

It cut out on me approaching a roundabout the other day. Id completely forgotten about it. Approaching a roundabout the engine stopped running altogether, "GEARBOX FAULT" on the dash but i managed to coast into a layby. As soon as turned the key it fired up again and hasn't done it again since.

Do you think they're related?

Anyone know anyone in the midlands who ll let me plug it in to a Nanocom?
 
jimllshiftit said:
It cut out on me approaching a roundabout the other day. Id completely forgotten about it. Approaching a roundabout the engine stopped running altogether, "GEARBOX FAULT" on the dash but i managed to coast into a layby. As soon as turned the key it fired up again and hasn't done it again since.

Do you think they're related?

Anyone know anyone in the midlands who ll let me plug it in to a Nanocom?
Click to expand...
Only a matter of time before one of the chains jumps it's sprocket then your in deep poo.
 
Oh well..... And there was me expecting a quiet weekend.

Any recommendations of where to get the bits from? I'm guessing this isn't going to be a cheap installation so I'd rather have quality parts for this.
 
jimllshiftit said:
Oh well..... And there was me expecting a quiet weekend.

Any recommendations of where to get the bits from? I'm guessing this isn't going to be a cheap installation so I'd rather have quality parts for this.
Click to expand...
I used Island 4x4. I'm sure Wammers posted that the crank sprocket was cheaper from BMW, it may even be in the technical archive.
 
This is what happens is the chains let go. Not to frighten you or anything. Get them done asap.
20190406_105130.jpg
 

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jimllshiftit said:
It cut out on me approaching a roundabout the other day. Id completely forgotten about it. Approaching a roundabout the engine stopped running altogether, "GEARBOX FAULT" on the dash but i managed to coast into a layby. As soon as turned the key it fired up again and hasn't done it again since.

Do you think they're related?

Anyone know anyone in the midlands who ll let me plug it in to a Nanocom?
Click to expand...

Ah. That doesn't sound so good although it could be a worn FIP. Cannot remember if yours is refurbed?

Have a look at the LZIR map. There's a member in Lichfield but cannot recall if he bought a Nanocom or not.

I priced up the chains and sprockets from Island-4x4 as about £300 maybe 5 years ago. Probably doubled since Brexit.
 
Grrrrrr said:
Ah. That doesn't sound so good although it could be a worn FIP. Cannot remember if yours is refurbed?

Have a look at the LZIR map. There's a member in Lichfield but cannot recall if he bought a Nanocom or not.

I priced up the chains and sprockets from Island-4x4 as about £300 maybe 5 years ago. Probably doubled since Brexit.
Click to expand...
I thought fuel quantity servo in the Fip but with the chains clattering changing them is cheaper.if you put the BMW part number in the bay there's a complete kit for about£ 226.dont know what the quality is like but the chains are a good make and comes with warranty.
 
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