question Here's a Head Scratcher.....................Humber 6 cylinder

[thedawnpatrol]

I will try and explain the symptoms...............

 

this is since having the engine rebuilt. i added the existing carb, dizzy and other ancillaries.

 

when first ran engine in chassis, after 15 mins, there was a metalic knocking noise and the engine stopped dead !

 

was something overheating/expanding ? this has since been tempromental with no rhyme or reason, but interestingly every time it has happened, an instant press of the starter and she fire up and runs fine.

 

Now that the truck is rebuilt, i have been able to road run it, again quite happy to go 2-3 or 4 miles, no problem, then there is this faint knocking progressinly getting louder then engine cuts i roll to a holt, press the starter and away we go again !

 

Now, if it were something in the engine, expanding with heat and tightening up enough to stop the engine, why would it spin on the starter and fire instantly with no knocking ?

 

if it was fuel starvation then it would cough and splutter and be hard to start instantly.

 

if it was timing / Distributor, then again would it miss fire ?

 

but non of these, what i don't understand is, what ever is causing the 'engine' to 'knock' ( i can not tell where it is comming from, by the time i get out of the cab, open the bonnet, it's too late) and stop the engine, why as i am still rolling in gear does it not fire on its own ? ( having said this, my instant reaction is to depress the clutch and roll to a holt, i have tried accelerating out of it, but still the engine dies.

i wondered if it was anything to do with the distributor bob weights ? but if it were, would it miss fire.

 

over to you guys

 

all answers gratefully apreachated !

 

Jules

[fesm_ndt]

Could it be knocking due to unleaded fuel? As differing temperatures can make this problem come and go.

 

Also sometimes if you time per the manual, which was for leaded fuel it is slightly different for unleaded.

 

Anyway I hope it is something easy like that, but if it's knocking, losing power sounds like maybe this.

 

As if knocking mechanically normally things break and you have metal flying around, oil leaks etc

[Rick W]

Not familiar with the engine, but is it chain driven?

[Locolines]

Is it pinking ?

[paulbrook]

Does it die or does it stop dead?

[andym]

I'd vote for something in the distributor. It sounds as though the timing is varying enough to make it pink then stop.

 

Andy

[Tony B]

Could the fuel be gassing Has the carb been rebuilt

[Locolines]

I am hoping its not oil starvation .......

[thedawnpatrol]

Thanks Guys

 

To be honnest, i have never herd anything 'pink' before, but it does sound like it could be that..........shall i just disconect the tiny pipe from the advance & retard and try it ?

 

it's certainly not throwing the timming out, i will check again tonight, the tapping starts gradually, gets louder, then cuts the engine, as said even by hitting the clutch and giving it more revs there is no responce.....

 

will report back tomorrow !

 

thanks for all your Thoughts...............i just don't want it to be a major engine problem !

 

 

Jules

[Richard Farrant]

Thanks Guys

 

To be honnest, i have never herd anything 'pink' before, but it does sound like it could be that..........shall i just disconect the tiny pipe from the advance & retard and try it ?

 

it's certainly not throwing the timming out, i will check again tonight, the tapping starts gradually, gets louder, then cuts the engine, as said even by hitting the clutch and giving it more revs there is no responce.....

 

will report back tomorrow !

 

thanks for all your Thoughts...............i just don't want it to be a major engine problem !

 

 

Jules

 

Hi Jules,

Disconnecting the vacuum advance pipe will only make that feature inoperable, but you still have the centrifugal advance weights under the base plate. Maybe they are jamming open. The fact that the engine cuts out after the noise is odd. I am surprised you have never heard an engine "pink" before, but it can give a metallic knock so could be that.

 

regards, Richard

[Pete Ashby]

This is a real long shot but I once had a simialr problem with a GMC engine. I'm not familiar with your distributor is it CAV or Lucas ? either way it may be worth checking the points base plate to see if it is firmly fixed to the rotor shaft.

 

The problem I had with the GMC engine was as follows: Engine would start and run and respond perfectly until fully warmed.

 

Then after a period of full throttle operation when the throttle was shut and then reopened to pull away it would start to miss fire an then die.

 

Once the engine cooled it would start and run perfectly again until everything warmed up again.

 

After a lot of messing about changing all the ignition components apart from the distributor quite by chance I noticed that the base plate was ever so slightly loose on the shaft ( a French rebuild, the base plate is only peened onto the shaft and it had worn)

 

The net result was that when every thing was hot the base plate would move into a fully advanced position and stick when the throttle was closed hence the missing and bad running.

[thedawnpatrol]

Well,

 

last night i took her for a good run, firstly fully warmed her up on driveway, a friend lent me a great tool, a laser 'point and read' tempreture reader, what ever you point it to, it reads the temp digitally.

before i started her, i took off the dizzt cap and adjusted the A & R to see if there was movement in the back plate, there was, so i set the A&R about half way. ( this was following some of your comments about this)

 

so armed with this tool i took several reading all over the engine, on the cylinder side at the front it was between 67c and 70c

mid way back was hotter at 80c then at the back was again 70c ( it varied slightly)

 

off we took, did 8 miles, no problem, i pulled over, engine ticking over ok, did another Temp check, much as before, but center of block showing slightly higher up towards 90c, where as each end was 75c - 79c.

 

i pulled over again after another 10 miles, all ok, checked again, simular temps, we then got home after another 5 miles, again all ok, not a hint of a problem.............in all about 20 miles.

 

i did keep to a steady max speed of 35/40 mph and kept revs low.

 

so, not anything exciting to report.............lets see how i get on driving to Evesham tomorrow, fingers crossed please..........

 

Thanks guys

 

Jules