Engine misfiring, likely suspects list

Yes, I guess we will just have to follow the diagnostic sequence and hope for the best outcome. Guess I was just trying to get a feel for most likely scenario in order to brace for financial impact......Which could be a project stopper in worst case scenario!
 
third engines said:
Diseasol only needs fuel and compression to fire, my dollar is on compression as fuel is present.
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Not necessarily if its not atomising. If the injector is simply squirting a jet of diesel in it is unlikely to burn properly. If its a fuel fault, which is most likely, and there isnt white diesel smog in the exhaust this suggests its passing neat diesel, the diesel isnt reaching the injector, or the injector isnt opening. But OPs engineer is following the well proven test sequence, as others have said, so it will be interesting to see what he comes up with.
 
points to ponder,

1. If the engine has a misfire, it WILL bounce about more. The mounts may still be old and tired but the excessive vibration isn't necessarily a symptom of tired old mountings.

2. If the "odd" cylinder has a functioning injector and is losing compression, where's the fuel going? Any unburnt fuel finding it's way into the exhaust should cause smoking.

3 it's unlikely that a single pump/injector will be mistimed. The pumps in the block are usually cam operated. I've never known a single cam to deteriorate much worse than the others on the same shaft.

+1 for your engineer's diagnostic process, do the "cheap" stuff first (fuel, valve clearances etc the move onto the expensive items like pump/injector combinations and head removal.)

Hope all goes well.
 
Topcat47 said:
points to ponder,

1. If the engine has a misfire, it WILL bounce about more. The mounts may still be old and tired but the excessive vibration isn't necessarily a symptom of tired old mountings.

2. If the "odd" cylinder has a functioning injector and is losing compression, where's the fuel going? Any unburnt fuel finding it's way into the exhaust should cause smoking.

3 it's unlikely that a single pump/injector will be mistimed. The pumps in the block are usually cam operated. I've never known a single cam to deteriorate much worse than the others on the same shaft.

+1 for your engineer's diagnostic process, do the "cheap" stuff first (fuel, valve clearances etc the move onto the expensive items like pump/injector combinations and head removal.)

Hope all goes well.
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Good points

My thoughts too about the vibration, hence we need to sort the misfire out first I guess before attending to that.

Regarding smoke in exhaust, it was unfortunately dark when we looked at the engine the other night, though my recollection from running it previously is that there was not significant smoke..We will check that over the weekend now
 
PaulRainbow said:
So it doesn't need atomised fuel ? How about air ? What about injecting the fuel in at the correct time ? Etc Etc
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So Paul, yes it does need all those you correctly quote. However, the big indication of un-atomised fuel has not been mentioned by the op which is usually unmistakeable. My post was no more than an sofa considered diagnosis of the situation as are all the posts.
 
third engines said:
So Paul, yes it does need all those you correctly quote. However, the big indication of un-atomised fuel has not been mentioned by the op which is usually unmistakeable. My post was no more than an sofa considered diagnosis of the situation as are all the posts.
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Are you referring to smoke In the exhaust? I will check properly per the weekend, but as I mention it was dark when I was down there so can't rule smoke out
 
Tim O said:
Are you referring to smoke In the exhaust? I will check properly per the weekend, but as I mention it was dark when I was down there so can't rule smoke out
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Given your description, catastrophic loss of compression on a single cylinder is unlikely. As we're all taking pot shots, i'll wager an injector fault.
 
PaulRainbow said:
Given your description, catastrophic loss of compression on a single cylinder is unlikely. As we're all taking pot shots, i'll wager an injector fault.
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Not even blown gasket or cylinder head/block crack? Tis why I would (at some stage) sniff for exhaust in the coolant. Most garages have the kit and it only needs taking the filler cap off to test.
 
But why would a head/block just crack out of nowhere? This engine was running fine ten months ago, and fine a week ago under no load.......Surely nothing has happened to crack a block?
 
Tim O said:
But why would a head/block just crack out of nowhere? This engine was running fine ten months ago, and fine a week ago under no load.......Surely nothing has happened to crack a block?
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That was more from armchair pontification rather than probability. Although my car is suffering from that, all I can think of is that I took a hill a bit keen from cold start.

My money at the moment is quite firmly on gunge in the injector.

I think the gallery here was hoping for a daily update, all this waiting for the weekend gives the gremlins too much playtime.
 
Dougal Tolan said:
Not even blown gasket or cylinder head/block crack? Tis why I would (at some stage) sniff for exhaust in the coolant. Most garages have the kit and it only needs taking the filler cap off to test.
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It could of course be a myriad of things, but the description doesn't sound any alarm bells for catastrophic mechanical failure. I think his mechanic sounds to be making the right noises, so look forward to hearing the true cause.
 
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