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Discussion Starter · #1 ·
Hello all,

New to the 4BT conversion world.

Just purchased a "90 GMC Sub 2500 4X4 with a "NEW" 4BT , and a (Redline rebuilt) auto(not sure which model) out of a 1 Ton dodge, thinking probably a 46RH since it has a shift lever coming up through the floor, coupled to a NP 205 professionally built by some performance place out in Cali, and has 4.10 gears with 285/65/18 tires.

Looks as though the engine label is missing (thinking it"s not really "NEW", but new reman), and not sure yet what fuel pump, or turbo it has. I'm hoping that maybe some can ID them by the attached Pic's

I purchased this as a non running vehicle, as the owner couldn't keep the batteries from going dead overnight.

In my complete optimism, I'm flying out to pick it up this coming weekend, and planning on driving it halfway across the country to get it home. Wish me luck......, I figure it was running when it was parked, so how hard can it be.(10-12 volts to the fuel solenoid, and fuel, and it should run, right?)

It looks to have a Larry B's fuel solenoid in it, and am thinking that it might be wired incorrectly(possibly not killing both hot leads), as they use the original GM ignition to start it, and push a button to shut it off. (anyone with any helpful hints in diagnosing?) I'm fairly mechanical, but pretty short in the electrical department.

The person that I'm buying it from told me that he had been driving it for a couple weeks no problem, went to get in it one day, and had just clicking. Replaced both batteries with 2 new Die Hard batteries, it fired right up and everything was good, until the next morning when he went out and it would not start. no clicking or anything.
He also tells me that he then being discouraged, and over his mechanical ability just decide to park it. he went out the other day after I committed to purchasing it, opened the door and the dome light came on, and he tried to start it. Apparently it acted like it wanted to turn over, but would not start.( it's been sitting now for a year since he last tried to start it).

Many thanks in advance for any helpful suggestions, I do appreciate it.

I plan on trying to make it a reliable rig with adequate power, and exceptional fuel mileage. The second item of business after I get it to run, is to install some kind of air cleaner before driving it any distance.

I am just short of overwhelmed by the amount of info on this site, so any pointers would be appreciated.

I'm thinking a intercooler(anyone have an idea of what intercooler would fit?),and maybe fuel spring and timing adjustment would be in order for starters, just unsure at this point what fuel pump and turbo are in it.(maybe someone can identify by the pics?)
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The electrical problem may be solved by removing all fuses, does it still discharge- then something shouldn’t be connected. As replacing fuses, soon will discover which fuse circuit is short to ground.

Trans could be a Dodge 47rh(94-95 only) or 47re(computer in the system). Rh has 3 pin connector, L side of engine, vertical disconnect, OD, LU. RE does not have this, Also 3 pin connector lower down on engine, horizontal disconnect-backup, neutral safety, RE has many pin connector here. Google each, easy to determine.

Ed in CO.
 

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If you can get him to charge the batteries during the week that would help you when you get there. fresh fuel filter or take off the one on there and drain it and refill it with fuel and make sure there's fuel in the tank. make sure to prime the injection pump to get fuel to it. if the injection pump has air in it then you might / probably need to bleed the lines to the nozzles / injectors. you will have to loosen the injection line nut on the injector to get fuel out of it then tighten the line and do the next either if it starts or when cranking.

as for the electrical drain you might take a quick look at the electric fan wiring and like previously said pull the fuses and do like said. when you get it running make sure to check the voltage to make sure its charging. if it is then you should be good once its running.

get a few things at the parts store for the journey oil, water coolant trans fluid new fuel filter and you might be good for the trip. safe travels.
 

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Discussion Starter · #5 ·
The electrical problem may be solved by removing all fuses, does it still discharge- then something shouldn’t be connected. As replacing fuses, soon will discover which fuse circuit is short to ground.

Trans could be a Dodge 47rh(94-95 only) or 47re(computer in the system). Rh has 3 pin connector, L side of engine, vertical disconnect, OD, LU. RE does not have this, Also 3 pin connector lower down on engine, horizontal disconnect-backup, neutral safety, RE has many pin connector here. Google each, easy to determine.

Ed in CO.
Ed,
Thanks for the suggestion about pulling the fuses, I had not thought of that.

I was thinking that I would start with a multimeter to see what if any voltage were in the batteries, (to see if the problem was battery or possible ignition related) and providing I can get it to run, check the alternator output.

I think at that point depending on the outcome I would probably go to pulling fuses as you suggested.

Does that seem somewhat of a good plan ?

I"ll have to look at the trans, and then google it if I have any further questions.

Thanks again.
Randy
 

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Discussion Starter · #6 ·
Looks like a nice setup. I would be worried taking a long trip right off. Does it have a EGT gauge?
I think it has a lot of potential, anyway.

I'm just crazy enough or cummins trusting enough to give it a go.

Not sure about the EGT gauge ,but was planning on putting one in ASAP, possible before I pull out with it.
I would sure feel better knowing were it's running at.
 

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Discussion Starter · #7 ·
If you can get him to charge the batteries during the week that would help you when you get there. fresh fuel filter or take off the one on there and drain it and refill it with fuel and make sure there's fuel in the tank. make sure to prime the injection pump to get fuel to it. if the injection pump has air in it then you might / probably need to bleed the lines to the nozzles / injectors. you will have to loosen the injection line nut on the injector to get fuel out of it then tighten the line and do the next either if it starts or when cranking.

as for the electrical drain you might take a quick look at the electric fan wiring and like previously said pull the fuses and do like said. when you get it running make sure to check the voltage to make sure its charging. if it is then you should be good once its running.

get a few things at the parts store for the journey oil, water coolant trans fluid new fuel filter and you might be good for the trip. safe travels.
Redark1,

Great suggestion. I'm thinking that he doesn't have the ability to charge them, but I haven't asked yet.

I was planning to stop by an auto parts store get filters, oil, coolant, and a basic tool kit , along with a test light and multimeter, etc

I'm optimistic that I wont have to go as far as bleeding the injectors, as it was running when he parked it, but I'm thinking it ultimately depends on the type and location of the fuel filter housing, and if I have any drain back of fuel while changing it.. Thanks for the low down on the injector bleeding, and pump priming procedure.

I will definitely take a look at the electric fan. Is there anything in particular that I should be on the lookout for? I'm encouraged that for the most part it doesn't appear as though there is a bunch of "rats nest" looking wiring. The gentleman had a respectable shop do all of the work on it, and has moved to a new town since then, so is unable to take it back to have them diagnose.
 

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Discussion Starter · #8 ·
I think it has a lot of potential, anyway.

I'm just crazy enough or cummins trusting enough to give it a go.

Not sure about the EGT gauge ,but was planning on putting one in ASAP, possible before I pull out with it.
I would sure feel better knowing were it's running at.
I'm thinking that there should be some kind of plug in the manifold that I could remove to install an EGT ?

Any suggestions on a good quality EGT gauge ?
 

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Looks like a decent build, except for the turbo intake, you might be able to rig up something temporary with a close rubber intake elbow and a cone filter... a egt gauge is a must since you will be pushing the motor to around 2100 with 32in diameter tires, 4.10's and a final drive ratio of 0.69 on a 47rh-re trans, that puts you around 70 mph and at 70 most other motorists will consider you impeding...!!! Isspro makes one of the best pyrometer available, they have been standard issue on the big trucks for decades... on the starting issue, make sure you have a good ground between the motor and the body-frame, I like to have two ground straps, motor to frame and frame to body, I have forgotten to reinstall straps on motor rebuilds and then experience hard or slow starting which will mimic dead batteries... or like your thinking, something going on with the fss, power to the fss should go thru a relay, I think it's like a 75 amp relay, the fss draws around 45 amps... safe travels...
 

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Discussion Starter · #10 ·
Looks like a decent build, except for the turbo intake, you might be able to rig up something temporary with a close rubber intake elbow and a cone filter... a egt gauge is a must since you will be pushing the motor to around 2100 with 32in diameter tires, 4.10's and a final drive ratio of 0.69 on a 47rh-re trans, that puts you around 70 mph and at 70 most other motorists will consider you impeding...!!! Isspro makes one of the best pyrometer available, they have been standard issue on the big trucks for decades... on the starting issue, make sure you have a good ground between the motor and the body-frame, I like to have two ground straps, motor to frame and frame to body, I have forgotten to reinstall straps on motor rebuilds and then experience hard or slow starting which will mimic dead batteries... or like your thinking, something going on with the fss, power to the fss should go thru a relay, I think it's like a 75 amp relay, the fss draws around 45 amps... safe travels...
bommersrule55.

Thanks for the info. Ive been looking at cold air intakes, and haven't found one that is generic enough yet. Do you have any idea what the O.D. of the cold side/air intake of that presumably stock turbo is ?

On the tire size/final ratio , I was thinking that i would probably to a 37" tire or so based on what I've read so far on the 4BT RPM sweet spot for fuel mileage being around 1800, and fuel mileage really starting to drop off at any thing over 2000 RPM's.(hopefully for your sake you wont be stuck behind me when I take the maiden voyage this coming weekend if the thing only tops out at 70). Lol.....

Thanks for the suggestion on the Isspro pyrometer, I'll look for one. Do you by chance if the 4BT has a plug in the manifold for the probe ?

I have had the same issues with ground straps before, but hadn't thought about that, and it will now be closer to the top of the list of things to start with.
 

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You've likely got an electrical fault bleeding the battery. You need to locate where that is happening. Likely suspect would be a fault in the alternator which wouldn't show up by removing fuses. Another possible would be the injection pump solenoid. If not wired correctly that unit can drain the battery. Those are the two most likely suspects. That current draw is pretty severe to bleed the battery so fast. One problem I see on that build is there's no intercooler. A stock P pumped 4bt always had one and if this one has been turned up any at all you're fighting against heat to make power. With any kind of boost level at all from the turbo, the compressed air can reach 300 deg F or more. Hot air makes poor power. Also, looks like that engine has a.n H1C turbo which is not what a P pump used. It should have an HX30W. The lack of an air cleaner system is a death notice for the turbo plus you're sucking hot air off the exhaust manifold. Here's a photo of what that engine should have looked like on the turbo side on an original install.
 

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bommersrule55.

On the tire size/final ratio , I was thinking that i would probably to a 37" tire or so based on what I've read so far on the 4BT RPM sweet spot for fuel mileage being around 1800, and fuel mileage really starting to drop off at any thing over 2000 RPM's.(hopefully for your sake you wont be stuck behind me when I take the maiden voyage this coming weekend if the thing only tops out at 70). Lol.....

Thanks for the suggestion on the Isspro pyrometer, I'll look for one. Do you by chance if the 4BT has a plug in the manifold for the probe ?
My truck will not go over 65 with excessive EGTs. (Unless down hill) My rpm is 2400 at 65. I generally cruise at 62 with EGTs of a 1000. My mpg is around 14-15. (Truck shaped like a brick.) So high rpms is not that bad for mileage, but I would be worried about hitting a long hill without a EGT. It is real easy to hit high numbers on a hill.

There is no stock plug for EGT that I know of. Hopefully, they already installed one.
 

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Discussion Starter · #14 ·
You've likely got an electrical fault bleeding the battery. You need to locate where that is happening. Likely suspect would be a fault in the alternator which wouldn't show up by removing fuses. Another possible would be the injection pump solenoid. If not wired correctly that unit can drain the battery. Those are the two most likely suspects. That current draw is pretty severe to bleed the battery so fast. One problem I see on that build is there's no intercooler. A stock P pumped 4bt always had one and if this one has been turned up any at all you're fighting against heat to make power. With any kind of boost level at all from the turbo, the compressed air can reach 300 deg F or more. Hot air makes poor power. Also, looks like that engine has a.n H1C turbo which is not what a P pump used. It should have an HX30W. The lack of an air cleaner system is a death notice for the turbo plus you're sucking hot air off the exhaust manifold. Here's a photo of what that engine should have looked like on the turbo side on an original install.
You've likely got an electrical fault bleeding the battery. You need to locate where that is happening. Likely suspect would be a fault in the alternator which wouldn't show up by removing fuses. Another possible would be the injection pump solenoid. If not wired correctly that unit can drain the battery. Those are the two most likely suspects. That current draw is pretty severe to bleed the battery so fast. One problem I see on that build is there's no intercooler. A stock P pumped 4bt always had one and if this one has been turned up any at all you're fighting against heat to make power. With any kind of boost level at all from the turbo, the compressed air can reach 300 deg F or more. Hot air makes poor power. Also, looks like that engine has a.n H1C turbo which is not what a P pump used. It should have an HX30W. The lack of an air cleaner system is a death notice for the turbo plus you're sucking hot air off the exhaust manifold. Here's a photo of what that engine should have looked like on the turbo side on an original install.
charr1355,

Thanks, I figured that after I get it running I would check the alternator output. Open to any suggestions on how to check for a fault in the alternator, and how to determine if the injection pump solenoid(assuming that your talking about the fuel shut off solenoid?) is wired correctly.

I am planning on trying to get some kind of air cleaner set up on it before driving (that's the biggest thing for me after diagnosing the starting problem). Any idea what the diameter is on the cold air side of that turbo?

Also planning on adding a charge air cooler once I get it back. Any idea of one that might fit or who might be able to
help me figure it out ? I'm not sure if it has been turned up at all(waiting for more info from the seller)

Do you think that the turbo( assuming it's an H1C like you think) would be okay to drive back home providing I get some kind of air cleaner on it?

My truck will not go over 65 with excessive EGTs. (Unless down hill) My rpm is 2400 at 65. I generally cruise at 62 with EGTs of a 1000. My mpg is around 14-15. (Truck shaped like a brick.) So high rpms is not that bad for mileage, but I would be worried about hitting a long hill without a EGT. It is real easy to hit high numbers on a hill.

There is no stock plug for EGT that I know of. Hopefully, they already installed one.
 

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Discussion Starter · #15 ·
My truck will not go over 65 with excessive EGTs. (Unless down hill) My rpm is 2400 at 65. I generally cruise at 62 with EGTs of a 1000. My mpg is around 14-15. (Truck shaped like a brick.) So high rpms is not that bad for mileage, but I would be worried about hitting a long hill without a EGT. It is real easy to hit high numbers on a hill.

There is no stock plug for EGT that I know of. Hopefully, they already installed one.
dreamin,

Thanks,

Bummer, on the no plug in the manifold. I'm assuming that you must drill and tap it ? I was planning to run it in that 1800-2000 RPM range on the way back just to air on the side of caution, if it doesn't have a pyrometer. Hopefully we wont irritate too many people for driving like an old lady. Lol.....

I'm planning on going with a 37" tire to hopefully get the gearing right (based on info supplied to me from another 4BT swaper in an earlier post) to keep the RPM's in that 1700-2000 range
 

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To check the electrical draw you need a meter that reads current flow. If you start unhooking things and it still shows a current draw, the alternator would be a prime suspect. If you disconnect it's charge wire from the system and the current draw stops then you've found it. If that doesn't stop it then it's got to be a source not controlled by the fuse block if you've remove it from the current circuit. Instead of disconnecting the fuse block, you'd want to remove individual fuses and see if the draw stops. If not, replace that fuse and try another one. Electrical bugs can test ones sanity some times. The old H1C turbo won't hurt anything but it's not the best performer. Cold air side of that turbo should be 3" unless someone stuck a Dodge H1C on there which would be 4". Hope they didn't do that because that is a terrible turbo for a 4bt. Be nice if the guy can tell you the model of the turbo. Don't think it's a WH1C or HX35W but can really see it with all those hoses in the way. If the turbo is the one I think, the EGT's shouldn't be much of an issue. Those turbos had a huge turbine housing to help get rid of excess heat.
 

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Sounds more like a faulty connection. Will not start next morning but still had life in the batteries after a year, then there is no excess draw on them. Possibly even a bad starter motor.
 

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bommersrule55.

Thanks for the info. Ive been looking at cold air intakes, and haven't found one that is generic enough yet. Do you have any idea what the O.D. of the cold side/air intake of that presumably stock turbo is ?

On the tire size/final ratio , I was thinking that i would probably to a 37" tire or so based on what I've read so far on the 4BT RPM sweet spot for fuel mileage being around 1800, and fuel mileage really starting to drop off at any thing over 2000 RPM's.(hopefully for your sake you wont be stuck behind me when I take the maiden voyage this coming weekend if the thing only tops out at 70). Lol.....

Thanks for the suggestion on the Isspro pyrometer, I'll look for one. Do you by chance if the 4BT has a plug in the manifold for the probe ?

I have had the same issues with ground straps before, but hadn't thought about that, and it will now be closer to the top of the list of things to start with.
idk if you have a threaded port on your exhaust manifold, most guys drill and tap somewhere before the turbo... I have a 90 degree hot pipe which is cast iron and it does have a threaded port for a pyro probe, some guys don't feel a after turbo probe gives a true reading, I'm up in the air about this, because the big trucks I've owned all had after turbo probes installed in the turbo down pipe... as does my 12v pusher motor home, it stays around 900-1000 on grades and 500-600 on flats... I found this tire size/rpm calculator on the spicer america site that is very user friendly, just remember your final drive ratio is 0.69 if your running a 47rh or re, this might help you when picking out tire size or a axle ratio change...
 

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Actually, Cummins recommends the pyro probe to be after the turbo. The reason for that is that if the probe should break it won't damage the turbine wheel. That in itself would be a very rare occurrence. Post turbo is fine but you have to keep in mind that reading will be 200-300 deg lower than pre turbo. I'd think 1000 deg post turbo would be the limit. Most guy shoot for 1000-1100 deg pre turbo. Another rule that many don't follow is when you come to a stopping point, don't just shut down the engine. You need to let it idle until that temp drops to around 500 deg or a bit lower. You see those big rigs sitting at the truck stop with engines idling is not to just waste fuel. They are saving their turbo from damage.
 

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Actually, Cummins recommends the pyro probe to be after the turbo. The reason for that is that if the probe should break it won't damage the turbine wheel. That in itself would be a very rare occurrence. Post turbo is fine but you have to keep in mind that reading will be 200-300 deg lower than pre turbo. I'd think 1000 deg post turbo would be the limit. Most guy shoot for 1000-1100 deg pre turbo. Another rule that many don't follow is when you come to a stopping point, don't just shut down the engine. You need to let it idle until that temp drops to around 500 deg or a bit lower. You see those big rigs sitting at the truck stop with engines idling is not to just waste fuel. They are saving their turbo from damage.
Yes, that makes perfect sense, and after your post I remember reading about that years ago, the possibility of probes breaking off, never had one do that, but why chance it?
 
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