Ambac Pump, port closing.

[Regent]

Just wondering how much pressure is required to open the delivery valve when checking pump timing without removing the delivery valve, pressure and flow. Does anyone have any specs on the pump system that Mack dealerships use to use, thanks for any replies.

[AZB755V8]

Normally the delivery valve is removed and a old holder and old cut injector line are used. The "dump" tube method is used to check timing this way. This can be done with compressed air and a glass jar with water in it. When the flow goes to a bubble using air that is port closure. Using fuel and a little pressure the flow will go to a drop. I have not heard of setting timing with the #1 delivery valve in place by just turning the pump to get pressure and flow. I can say it is over 1000psi to open a delivery valve. There are other ways to check timing on a Bosch pump but it is done with a timing light tool. Most Mack engine manuals have a few pages on the different ways to set timing as well. Hope this helps.

[fjh]

It takes aprox 2500-3000 psi to lift the valves off there seats ! I highly doubt it would be worth  buying  a pump and finding one cheap enough to  do this job once not worth your while! Your better removing the delivery valve and blo timing it! we have the tool at work  Its a nuisance to assemble and use Much faster  to blow time! just saying!

[Mack Technician]

Had a road call for a guy who need me to time a pump he installed. The port closure was screwing up and machine wasn't doing it for me. Called my shops "Mack old timer" and stepped through it again with him, having done it myself a dozen times. I was doing it right, but something was wrong with either my side or the pump side. Told customer you need to let us return tomorrow morning to complete this once we figure out what's going on. He was the shop's mechanic, he was watching me the whole time. Next morning he called and said "don't come, I got it going, runs great". I asked what he did. He said "I got it set using the priming pump". Two weeks later I was replacing his piston that had a hole burned through it. He made the situation much worse. Make sure you get it right.   

[AZB755V8]

2 hours ago, Mack Technician said:

Had a road call for a guy who need me to time a pump he installed. The port closure was screwing up and machine wasn't doing it for me. Called my shops "Mack old timer" and stepped through it again with him, having done it myself a dozen times. I was doing it right, but something was wrong with either my side or the pump side. Told customer you need to let us return tomorrow morning to complete this once we figure out what's going on. He was the shop's mechanic, he was watching me the whole time. Next morning he called and said "don't come, I got it going, runs great". I asked what he did. He said "I got it set using the priming pump". Two weeks later I was replacing his piston that had a hole burned through it. He made the situation much worse. Make sure you get it right.   

Pump timing is nothing to play with and think it is right. I admit I do advance the timing a few degrees in my stuff but after that it can lead to big problems. This guy had the timing way off and the truck ran like a wild dog for a short time but putting a hole in a piston with just timing, it must have been a whole lot??  Know piston failure can be done with more fuel and added timing to it. Just for my education, I learn from BMT also.

[theakerstwo]

For many years we used the primer pump and removed the delivery  valve spring.Most of us that worked on mack had a extra primer pump to use with those that did not have one.I have not used the electric pump to upseat the valve but I read in a mack manual one time that it was a 400 psi pump.I have used the air to time but to me its much easy to use the primer pump but ant saying its better.I never liked advancing the timing more that 2 degrees.

[fjh]

On 4/25/2019 at 7:24 AM, Mack Technician said:

Had a road call for a guy who need me to time a pump he installed. The port closure was screwing up and machine wasn't doing it for me. Called my shops "Mack old timer" and stepped through it again with him, having done it myself a dozen times. I was doing it right, but something was wrong with either my side or the pump side. Told customer you need to let us return tomorrow morning to complete this once we figure out what's going on. He was the shop's mechanic, he was watching me the whole time. Next morning he called and said "don't come, I got it going, runs great". I asked what he did. He said "I got it set using the priming pump". Two weeks later I was replacing his piston that had a hole burned through it. He made the situation much worse. Make sure you get it right.   

Glen 400 psi sounds a little low how ever it does make some sense the pressure would have to be lower than the injectors cracking pressure! Tech ,That said  the guy with the failed piston likely had a bad injector to add to the advanced timing issue, we once had an engine come to the shop pump installed by the owner and all 8 pistons were burned up by a ill timed pump! On The Timing subject , I have used the remove the delivery valve method with a little different twist ,for years and it never failed me once !The method I was taught  as follows ! remove #1 Delivery spring and needle valve reassemble hold down nut to pump , remove the inlet fuel line to pump make up a #6 one ended fuel line to fit on to the inlet Set the engine on the suggested  timing mark  Loosen the pump slot bolts leaving the top one snug on install  loosen that snugged bolt after the pump is on  and simply blow thru the hose you installed on the inlet and turn the pump till you can't blow or just see the tiniest amount of bubbles  at the #1 line connection on the pump  and simply lock it off at that point! Then test your set by turning the engine back a 1/4 turn and move back to the prescribed timing mark! 12 -24 degs  depending on the model and year! It's fun to see everyone's different methods of getting it done  !😁

The above method is best used when installing a new or reman pump as everything is off anyway and can be done with out getting fuel allover the place or just hooking up minimal lines! 

Edited April 26, 2019 by fjh

[Mack Technician]

58 minutes ago, fjh said:

Glen 400 psi sounds a little low how ever it does make some sense the pressure would have to be lower than the injectors cracking pressure! Tech ,That said  the guy with the failed piston likely had a bad injector to add to the advanced timing issue, we once had an engine come to the shop pump installed by the owner and all 8 pistons were burned up by a ill timed pump! On The Timing subject , I have used the remove the delivery valve method with a little different twist ,for years and it never failed me once !The method I was taught  as follows ! remove #1 Delivery spring and needle valve reassemble hold down nut to pump , remove the inlet fuel line to pump make up a #6 one ended fuel line to fit on to the inlet Set the engine on the suggested  timing mark  Loosen the pump slot bolts leaving the top one snug on install  loosen that snugged bolt after the pump is on  and simply blow thru the hose you installed on the inlet and turn the pump till you can't blow or just see the tiniest amount of bubbles  at the #1 line connection on the pump  and simply lock it off at that point! Then test your set by turning the engine back a 1/4 turn and move back to the prescribed timing mark! 12 -24 degs  depending on the model and year! It's fun to see everyone's different methods of getting it done  !😁

The above method is best used when installing a new or reman pump as everything is off anyway and can be done with out getting fuel allover the place or just hooking up minimal lines! 

Never used air, that’s new to me. We had an electric flow pump loop set-up and that was what I was taught as the single method.

It’s been 12 years....., but didn’t you guys also remove the puff limiter and jig it with the solid preset dummy?  

[fjh]

Never had to worry about this with the afore mentioned method as nothing was connected other than throttle lever

[JoeH]

Don't remember which pump style it was, but we timed a fuel pump last year using a snow plow pump. Our Mack book said to supply about 700-750psi of diesel to the pump and put a dummy line in place of #1? Injector line. 

We cleaned out my old Western Unimount plow pump, (still wired to the truck) put a pressure gauge on it and adjusted the pressure to 700 or so, filled it with diesel, hooked it up through one of the angle ports, and set the timing that way. 2nd? Time my dad's timed a fuel pump that way at least. Last one I know about was in the late 80s, and we're still driving that truck like we stole it.

Both engines are endt676, ones a '76 the other a '79

Edited April 26, 2019 by JoeH

[JoeH]

Make sure snow plow pump housing is nice and clean, lots of stuff builds up over years of use. Flush it out real well.

[Mack Technician]

Clever use of what you have Joe. At the end of the day you don’t have a flow pump tool sitting in your way (fuel rotting) till you need it again in 6 years.

Edited April 26, 2019 by Mack Technician