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Rob

Puff Limiter On V8-325 Maxidyne?

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Did Mack use a "puff limiter" on this engine? The engine runs very well with the pump governor (idle speed) recalibrated, but really smokes a lot when into the throttle. I've seen no air line as in an inline engine to the intake manifold.

I keep the truck inside of my heated building and before starting the engine, use shop air to charge the tanks. That way I can start the engine as the overhead door is raising, and get outside before someone cannot breath. When the engine is warmed up at idle, a slight "blip" of the throttle sends a thick smoke cloud out of the exhaust. When accelerating, a thick, dual path of smoke remains behind me. There is a buildup of carbon soot in the stacks also.

Do keep in mind the engine has not been "worked" in many years and has a lot of idle time on it.

Thanks,

Rob

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im not up on the old V8s Rob. i want to say the E9 has a puff but its a newer engine. Does your pump have an air line to the front or back of the pump. is the pump a "V" or inline ?

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im not up on the old V8s Rob. i want to say the E9 has a puff but its a newer engine. Does your pump have an air line to the front or back of the pump. is the pump a "V" or inline ?

Hi Trent, it is a "V" style pump, but has no air lines in the front, or rear.

Rob

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Did Mack use a "puff limiter" on this engine? The engine runs very well with the pump governor (idle speed) recalibrated, but really smokes a lot when into the throttle. I've seen no air line as in an inline engine to the intake manifold.

I keep the truck inside of my heated building and before starting the engine, use shop air to charge the tanks. That way I can start the engine as the overhead door is raising, and get outside before someone cannot breath. When the engine is warmed up at idle, a slight "blip" of the throttle sends a thick smoke cloud out of the exhaust. When accelerating, a thick, dual path of smoke remains behind me. There is a buildup of carbon soot in the stacks also.

Do keep in mind the engine has not been "worked" in many years and has a lot of idle time on it.

Thanks,

Rob

sounds like everything is just like it oughta be...or like it used to be anyway.I used to like to look in my mirror and see a big cloud of smoke every time I changed gears in that 5 speed.

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sounds like everything is just like it oughta be...or like it used to be anyway.I used to like to look in my mirror and see a big cloud of smoke every time I changed gears in that 5 speed.

I agree but this is thick enough to thoroughly blacken whatever is on a trailer behind you. It would probably even make persons in a following car hack and cough!

Rob

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After playing with Stans E9/500 hp V8, I can understand the smoke issue. The little video I posted shows the thick black smoke with just a quick swat of the throttle. I could imagine under a good pull!! LOL!

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After playing with Stans E9/500 hp V8, I can understand the smoke issue. The little video I posted shows the thick black smoke with just a quick swat of the throttle. I could imagine under a good pull!! LOL!

I just bought a new camera for the shop that takes movies. I'm gonna teach myself to use it and then get a video posted so everybody can see what this thing emmits from the stacks!

Rob

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how is the boost from the turbo? my guage reads about 1 lb of press just at idle. if the a/f ratio is way out of wack it can blow alot of black under a good pull. Before i found that i had a bad turbo on my truck i was throwing a good trail even with the puff working. can you check your fuel retern press?

Trent

post-17-1202062575_thumb.jpg

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how is the boost from the turbo? my guage reads about 1 lb of press just at idle. if the a/f ratio is way out of wack it can blow alot of black under a good pull. Before i found that i had a bad turbo on my truck i was throwing a good trail even with the puff working. can you check your fuel retern press?

Trent

Hi Trent, the turbocharger is new as per the "moron" I purchased the truck from. I'm sure you know the deal there as I've posted it. I did have the numbers checked and it is correct for the engine. Only pulled one load with it and the boost was about 22-25psi under hard acceleration with an amazing amount of smoke, (much thicker than your picture).

I've not checked into the nozzels or anything yet but the air filter element is new, and airways clear.

The engine is loaded up from all of the idle time and runs very well when warmed up. It is damn near impossible to start at 30 degrees outside unless plugged in and then still takes nearly two minutes to hit on all eight cylinders. But it is very powerful when loaded! Of course I'm comparing to a END-673 in a B model!!

I'm going to try to post some photos this afternoon if I can teach myself how to use the camera.

Rob

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Well boost seams ok. that kind of press is very good for an olddog. i get 24-28 with the fuel turned up on my 6cyl. i guess you need to check the fuel return and injectors now? it sometimes only takes one bad injector to throw alot of smoke. My RS throws clouds only when i have the puff off(dash switch operated)When its operating normal it has a grey hint from the stacks after each shift. Hopefully FJH on this site sees this. He knows the old V8s pretty well.

my 6cyl barly starts below 30 deg. plugged in she fires right off unless its -0 and below then she chuggs a little.

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:SMOKIE-RT: My 866 V8 had a Puff limiter on it at one time . I think the 865 s probably did to.

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:SMOKIE-RT: My 866 V8 had a Puff limiter on it at one time . I think the 865 s probably did to.

Where did the air line(s) attach? Mine has no plugs, or open fittings anywhere on the pump.

Rob

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Rob

i just looked in my mack service book that the mack museum sent me for the old B model and found something that maybe the issue but not shure?

Page 4-11 it does not show the "v"style pump but discribes a device that advances /retards the fuel timing per "x" RPM. just a thought.. i dought its something you have on your pump. but....

Trent

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Rob

i just looked in my mack service book that the mack museum sent me for the old B model and found something that maybe the issue but not shure?

Page 4-11 it does not show the "v"style pump but discribes a device that advances /retards the fuel timing per "x" RPM. just a thought.. i dought its something you have on your pump. but....

Trent

I've got a TS-442 series manual that was printed in 1978, (the truck is a 1977) and will do some reading in it. I'm wondering if the timing retarder is a newer version of "Syncrovance" that the inline engines used when natural asprirated?

Rob

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Rob

i just looked in my mack service book that the mack museum sent me for the old B model and found something that maybe the issue but not shure?

Page 4-11 it does not show the "v"style pump but discribes a device that advances /retards the fuel timing per "x" RPM. just a thought.. i dought its something you have on your pump. but....

Trent

Your set up is the same as Trents on his six!

There is a reversing relay suposed to be mounted near the left front inlet manifold and there Would have been a A bimbo slave on the rh rack end at the front of the fuel pump! if you don't see anything there its all likly been removed!Any Mack engine equiped with AMBC fuel pumps will have this stuff on it six or 8 cyl the reversing relay is the only diffrence on them you HAVE to have the V8 one for your aplication! Don't remember the no,s but the last digits in the part no must contain P10. Also there is a shim set for the bimbo slave it has a measurment!!! BUT having said that You just want to trim back the smoke NOT eliminate it SO simply space it out with 1 - 9/16 flat washer!

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Your set up is the same as Trents on his six!

There is a reversing relay suposed to be mounted near the left front inlet manifold and there Would have been a A bimbo slave on the rh rack end at the front of the fuel pump! if you don't see anything there its all likly been removed!Any Mack engine equiped with AMBC fuel pumps will have this stuff on it six or 8 cyl the reversing relay is the only diffrence on them you HAVE to have the V8 one for your aplication! Don't remember the no,s but the last digits in the part no must contain P10. Also there is a shim set for the bimbo slave it has a measurment!!! BUT having said that You just want to trim back the smoke NOT eliminate it SO simply space it out with 1 - 9/16 flat washer!

Here are a few photos of the engine. I cannot find evidence of anything being removed by looking at the pump.

Thanks

Rob

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I don't know anything about a v-8 pump but does anyone know whats under those two caps on the end of the pump,maybe some kind of manual rack adjustment.

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:SMOKIE-RT: The 375 V8 I have here has silicone covering the cap on the right side cap. I was told before that that was something to do with the puffer on that pump. I never took the silicone off though to have a peek. Mine used to belt out thick black smoke too, and sometimes an uneven flutter or miss at mid rpms. When we did a bearing roll a few years ago there were two rod bearings that had the top inserts worn and the other six were like new, so we decided to pull the injectors out and snap test them. Those two injectors were half dead , globbing not spraying like they should. we put 8 new injectors in it and she ran nice and smooth and got rid of my smoking problem too. I'll lhave a look on the spare injection pump I have when I go out to the shop this afternoon and take a peek at it, I'm pretty sure that cap has silicone on it , I'll peel it off and let you know what I find.

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:SMOKIE-RT: I looked at my spare pump for a 375 this afternoon, and found that the cap on the right side (passenger side) on it has an actual plug in it that looks like you probably could have had an airline attached to it at some time. I took off the two screws holding the cap on an found the cap was sealed with an o-ring, and under that appears to be a plunger assembly similar to the aneroid valve setup on the newer Robert Bosch injection pumps only without a diaphram. It also has a slot in the end that looks like you might be able to adjust it. I also took a look under the other cap and there is a similar type of plunger under it also but the cap on it is solid no place for fitting. I assume that the one that is on my complete engine just has the cap plugged with silicone instead of using a plug. My guess is that that might be wher the puff limiter is supposed to go. My 375 is a 1974 and I was told by a mechanic at the local dealer up here who actually worked on a couple of these engines when they were new and he said they were equiped with a puffer.

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:SMOKIE-RT: I looked at my spare pump for a 375 this afternoon, and found that the cap on the right side (passenger side) on it has an actual plug in it that looks like you probably could have had an airline attached to it at some time. I took off the two screws holding the cap on an found the cap was sealed with an o-ring, and under that appears to be a plunger assembly similar to the aneroid valve setup on the newer Robert Bosch injection pumps only without a diaphram. It also has a slot in the end that looks like you might be able to adjust it. I also took a look under the other cap and there is a similar type of plunger under it also but the cap on it is solid no place for fitting. I assume that the one that is on my complete engine just has the cap plugged with silicone instead of using a plug. My guess is that that might be wher the puff limiter is supposed to go. My 375 is a 1974 and I was told by a mechanic at the local dealer up here who actually worked on a couple of these engines when they were new and he said they were equiped with a puffer.

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:SMOKIE-RT: I looked at my spare pump for a 375 this afternoon, and found that the cap on the right side (passenger side) on it has an actual plug in it that looks like you probably could have had an airline attached to it at some time. I took off the two screws holding the cap on an found the cap was sealed with an o-ring, and under that appears to be a plunger assembly similar to the aneroid valve setup on the newer Robert Bosch injection pumps only without a diaphram. It also has a slot in the end that looks like you might be able to adjust it. I also took a look under the other cap and there is a similar type of plunger under it also but the cap on it is solid no place for fitting. I assume that the one that is on my complete engine just has the cap plugged with silicone instead of using a plug. My guess is that that might be wher the puff limiter is supposed to go. My 375 is a 1974 and I was told by a mechanic at the local dealer up here who actually worked on a couple of these engines when they were new and he said they were equiped with a puffer.

Well today I found out a few things. First off my engine is not original to the truck. I had my parts supplier chase down the engine serial number and it was fitted to a 1975 truck; mine is a 1977. The pump is also certified for a 1975 engine as stamped. It also had the "puff limiter" and "torque limiter" from the factory. The air cylinder is still on the trans, but the air line just hangs loose and unconnected. The injection pump has a plug in the end, (like yours) but I did not take it apart. The reversing valve, hose, and air cylinder are long gone. It is also stamped: PLE .857 which is the "puff limiter extension. The Mack service manual, (TS-442) has a very informative section on how this setup worked; Pretty slick for no electronics involved.

I did make an appointment to have the injectors looked at on Friday. I will pull them out and they will look at them while I wait. I was surprised to see the "crack pressure" so high at 3850 psi. Most engines I've been around are at 2300 psi and lower.

I really appreciate all the help with this thread. I probably won't install the "puff limiter" back onto the engine unless I can't get the smoke down by other means.

Thanks again!

Rob

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Well today I found out a few things. First off my engine is not original to the truck. I had my parts supplier chase down the engine serial number and it was fitted to a 1975 truck; mine is a 1977. The pump is also certified for a 1975 engine as stamped. It also had the "puff limiter" and "torque limiter" from the factory. The air cylinder is still on the trans, but the air line just hangs loose and unconnected. The injection pump has a plug in the end, (like yours) but I did not take it apart. The reversing valve, hose, and air cylinder are long gone. It is also stamped: PLE .857 which is the "puff limiter extension. The Mack service manual, (TS-442) has a very informative section on how this setup worked; Pretty slick for no electronics involved.

I did make an appointment to have the injectors looked at on Friday. I will pull them out and they will look at them while I wait. I was surprised to see the "crack pressure" so high at 3850 psi. Most engines I've been around are at 2300 psi and lower.

I really appreciate all the help with this thread. I probably won't install the "puff limiter" back onto the engine unless I can't get the smoke down by other means.

Thanks again!

Rob

Judging by the color of the engine it is a 325 maxidyne!The bimbo is not present but could be installed if you wanted to go that far!You would simply remove the plug on the right hand rack and install the bimbo slave and some shims and add in the reversing relay!

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Judging by the color of the engine it is a 325 maxidyne!The bimbo is not present but could be installed if you wanted to go that far!You would simply remove the plug on the right hand rack and install the bimbo slave and some shims and add in the reversing relay!

I pulled the nozzles out this morning and off to the pump shop I went. Not a single one of the eight was within spec. I don't recall how many were popping at under 3000psi but not one was suitable for reuse as is. Glad I parked the truck out of the way in the shop cause it will be about a week before they are done and come back. The spray pattern on four of the eight was for shit, two dribbled, one had a hole plugged solid, and one barely sprayed!

I would assume that the engine should run quite a bit better next week without quite so much smoke. Hard to believe it ran so well as is.

Rob

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Glad you found part of the problem!

let us know how the new nozzels work out.

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I pulled the nozzles out this morning and off to the pump shop I went. Not a single one of the eight was within spec. I don't recall how many were popping at under 3000psi but not one was suitable for reuse as is. Glad I parked the truck out of the way in the shop cause it will be about a week before they are done and come back. The spray pattern on four of the eight was for shit, two dribbled, one had a hole plugged solid, and one barely sprayed!

I would assume that the engine should run quite a bit better next week without quite so much smoke. Hard to believe it ran so well as is.

Rob

Good thing you got those injectors out of there Rob.

Next thing you know, a piston would have a hole melted through it.

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