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Can a VW pump top work with a 12mm cummins pump?
by
theman53
on 07 Dec, 2011 20:57
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I have a 12mm bosch pump off a cummins 4b engine. It is leaking on the top gasket. I drove it a couple days and wanted to die the way the governor was...guys that want a lopey idle will soon change their tune if they ever have to drive it. ANYHOW, question is now that I ripped it off the car can I put the VW pump top on the 12mm cummins pump with no mods and it work? I am wondering if I would need more spring or do the gov mod and call it good or if it wouldn't like the 1.6 governor spring assembly at all.
Does anyone know if both pumps have the same weighted governor fly weights? That would probably make the biggest difference.
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#1
by
CRSMP5
on 07 Dec, 2011 23:39
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i just did a gov mod.. 3-4mm of washers on my rover pump.. its stock red line supposedly 4k... i pull way more then 5k now.. and no surge..
IMO simple to try a gov mod 1st... if that sux.. then try to use a vw gov set up.. its all science IMO and when you find a what works.. post it up dso i can say you rwelds look like crap..
ohhh wait... no welding required...
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#2
by
theman53
on 08 Dec, 2011 04:52
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The govenor off the cummins pump had already been modded to rev around 5,000. The problem is the surge at idle. From what I gather it is an uncaged govenor and drives more like a truck than a car. It is weird as hell to put my foot down, nothing happen then it takes off. Or on a hill leave your foot in one spot and when more load comes it just picks it up for you and pulls the hill at the same rpm. The part I absolutely hated was when in 5th at just above idle speed it would surge like crazy. Shudder if you will, with very little pedal input and once that started you couldn't just floor it and make it stop. If you floored it then it would get worse until it got well into the rpm range. Whenever the same rpm and less pedal wouldn't make it do it if it hasn't started surging. The only way to make it stop with out rattling your brains was to downshift and give it tons more pedal. That made it almost a drag car only kind of ride. Which it did run good and had good pickup, but I daily this thing and IT SUCKED.
FWIW there is only 1 gov spring on this pump. Completely different than the 2 or 3 spring setup that VW has in its pump. Might be an area I could try to weld...hadn't thought of that
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#3
by
R.O.R-2.0
on 08 Dec, 2011 07:41
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The govenor off the cummins pump had already been modded to rev around 5,000. The problem is the surge at idle. From what I gather it is an uncaged govenor and drives more like a truck than a car. It is weird as hell to put my foot down, nothing happen then it takes off. Or on a hill leave your foot in one spot and when more load comes it just picks it up for you and pulls the hill at the same rpm. The part I absolutely hated was when in 5th at just above idle speed it would surge like crazy. Shudder if you will, with very little pedal input and once that started you couldn't just floor it and make it stop. If you floored it then it would get worse until it got well into the rpm range. Whenever the same rpm and less pedal wouldn't make it do it if it hasn't started surging. The only way to make it stop with out rattling your brains was to downshift and give it tons more pedal. That made it almost a drag car only kind of ride. Which it did run good and had good pickup, but I daily this thing and IT SUCKED.
FWIW there is only 1 gov spring on this pump. Completely different than the 2 or 3 spring setup that VW has in its pump. Might be an area I could try to weld...hadn't thought of that
Lucas, i believe all the cummins pumps had single spring, un-caged governors..
the VW has a 3 stage caged governor..
dunno if there interchangeable, but you could try it! i know the un-caged governor would drive me nuts..
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#4
by
burn_your_money
on 11 Dec, 2011 07:08
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I have often dreamed of building a pump with an uncaged governor. Your problems might be coming from the heavier spring used to increase the RPMs.
Isn't it a 2 spring though? One small one for idle and then the large one for everything else?
I think you can swap on the VW governor and LDA.
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#5
by
R.O.R-2.0
on 11 Dec, 2011 09:58
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I have often dreamed of building a pump with an uncaged governor. Your problems might be coming from the heavier spring used to increase the RPMs.
Isn't it a 2 spring though? One small one for idle and then the large one for everything else?
I think you can swap on the VW governor and LDA.
just as long as the top of the fulcrum plate has the accomodations for the VW governor assy..
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#6
by
RadoTD
on 11 Dec, 2011 10:24
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I think it might be a 2 spring caged governor and the only reason I say that is because my friend's 4BT ranger will dump fuel in when the rpm's drop below what the idle is set at. As far as I understand, it's one of the governor springs that does that. He can drop the clutch in 2nd without hitting the gas and it'll pull away
Also, higher rpm springs are available. There are a few performance diesel shops near me that can get 3600 and 4200rpm springs. They might be able to get a 5000 or 5500rpm spring as well, they'd just give me a real funny look if I asked for one! If that's your only hold up, I can do some digging for you if you'd like!
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#7
by
theman53
on 11 Dec, 2011 13:05
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The guy I bought it from got a 5,000 RPM spring and it is one single spring. I have an N/A pump on now so it isn't in emergency status. I would like to build one of my aaz engines and put that pump on it eventually.
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#8
by
R.O.R-2.0
on 12 Dec, 2011 09:58
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The guy I bought it from got a 5,000 RPM spring and it is one single spring. I have an N/A pump on now so it isn't in emergency status. I would like to build one of my aaz engines and put that pump on it eventually.
just like i figured.. im used to seeing 1 single spring in those cummins pumps..
if the top of the fulcrum plate is the same, swap in a VW governor and be happy
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#9
by
theman53
on 13 Dec, 2011 04:51
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It looks similar, but I don't know for sure. I want someone to tell me they did it before. I wish I had someone who wanted to test this pump to get it running on a known good engine and send it back to me. I am pretty sure now that I found that it had a missing bolt leaking fuel like crazy and fixed that, it may run just fine. I still don't think I would like the governor setup, but I think some of the surging and drivability issues would be fixed with the leaks fixed.
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#10
by
whoabeats
on 17 Mar, 2012 08:30
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Reviving an old post. I dont know if this issue was ever resolved, but I am working on an ahu that will sport a 4bt pump. I have looked at changing over just the governor in order to have the caged set up over the single spring that I believe is on most cummins pumps. In order to run the vw gov you must use the vw top plate. Because my vw pump is junk compared to the condition of the cummins pump. I now need to investigate to see if I can swap over all the springs from the cummins pump top to the vw. They are different parts but they serve the same purpose.
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#11
by
theman53
on 17 Mar, 2012 12:11
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Libby would know if anyone does.
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#12
by
camboscams
on 18 Mar, 2012 13:19
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Very interested in the outcome of this, due to the fact that i have a 4bt that i am building and it has a constant speed governor and it is a non-turbo ve pump on a turboed engine.