Rebuilt Perkins 4-108 Nightmare

[Mark Zarley]

Timing the pump is pretty straight forward. First rotate the eng untill the intake valve on #1 cylinder just closes, continue rotating (compression stroke) until you line up your timing mark ( could be on the front of the crank, or they could be on your flywheel) on the correct degrees, maybe 20 deg before TDC . You have now timed the eng to when the inj is ready to atomize. Next rotate the driven gear on the end of your inj pump so the timing mark on it line up with the timing mark on the drive gear. Here is the trickest part, the two gears are slanted , as you install the pump the pump gear will rotate making your perfect alignment of the marks be off by a tooth. So you have to allow for this , if it is right the marks will line up perfectly. So , time the eng first , then time the inj pump to the eng.

[johnar]

MarK one thng you said about being one tooth off is very true, this is the case here.

I also seen someone said they did not understand why i am woried about the pump if io still have a leak.

Well I fixed all leaks last night after the sun went down, now to the update.

Talk to L&J and they are coming out to remove the pump and bench test or set it and then reinstall in the boat Free.

Also had more good news this morning, the new A/C heat unit I got in May also and went out is being replaced Free and a refund for what I paid for a service call.

all and all turning out to be a good day.

Oh after fixing all leaks the motor is running better under load but still not the way I would trust along with knowing the timing is off brings the reason L&J is removing the pump.

Dutch

[YourOldNemesis]

The inj pump needs to be timed to the engine, not taken off and fixed separately.

[Pete the Cat]

I have a question about the responses.....I thought that---on most multiple cylinder engines the fuel lines from the pump to the injectors are exactly the same diameter and length (they have to be in order for the pump to run correctly, right??? because otherwise the pump would be out of time) even though they may be factory bent in very different directions to reach injectors. And within reason, why could you not rebend (without kinking), them?? The fuel is under very very high pressure here and has to arrive at each cylinder in the sequence at exactly the right time which after the pump is determined by the diameter and length of the line. Just trying to increase my understanding here of diesel theory and practice.

[s/v 'Faith']

Ray,

You are right on about the 'exact diameter, and lenght'. The lines are bent at the factory to bend without decreasing the diameter... and without producing fatigue. There are other considerations also, like the length between the bends must be 'tuned' to avoid sympathetic vibration. Mercedes automotive lines come with rubber dampers from the factory, some 'mechanics' will remove these as they have no apparent purpose. On those cars, the lines break from the vibration.

In the case of the OP, I would recommend (as others have said) fixing the known leak first (always) and then invest in the new lines. If they do not need to be replaced now, they will break some time.

Oh, and NEVER let that idiot who 're-bent' the lines aboard the boat ever again!

Originally Posted by Pete the Cat

I have a question about the responses.....I thought that---on most multiple cylinder engines the fuel lines from the pump to the injectors are exactly the same diameter and length (they have to be in order for the pump to run correctly, right??? because otherwise the pump would be out of time) even though they may be factory bent in very different directions to reach injectors. And within reason, why could you not rebend (without kinking), them?? The fuel is under very very high pressure here and has to arrive at each cylinder in the sequence at exactly the right time which after the pump is determined by the diameter and length of the line. Just trying to increase my understanding here of diesel theory and practice.

[Chief Engineer]

You do not rebend steel diesel injector lines.

You do not bend them when removing.

To do so results in cracking the steel line.

Each line is made uniquely for each cylinder.

And make sure that the name of that "guy" gets around....he is a moron

Oh, and NEVER let that idiot who 're-bent' the lines aboard the boat ever again

[shakey doug]

Very interesting posts, there certainly are some cowboys out there that need to be exposed. A couple of statements need to be clarified, 4108 fuel pumps are driven via a master splined shaft that can only be fitted in one position; the length of hp lines are not always the same, as the pump is a positive displacement type, flow rates are so low that line friction does not have a affect for calculation purposes.