Attempt at test running a Magnum

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tcanin00

tcanin00

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I want to test run the engine before putting it in the Dart. Since I pulled the entire harness from the 1994 Dakota, I hooked everything up and wired together all of the grounds.
It cranks and is firing, but isn't getting fuel. A few things I think it could be is fuel level, fuel pressure, and something not connected or grounded.
1. Fuel level-I only had a gallon or so to put in the 1992 B250 fuel tank. The pump primes with the key on and is pumping.
Could the amount of fuel not be enough to be picked up and pressurized?
2. Fuel pressure-The pressure regulator is leaking, it's wet from the outside and there doesn't seem to be much pressure in the fuel rail at the Schrader valve.
Could the leaking valve be allowing pump pressure to bleed off?
3. Wiring/components/grounds-The harness is laid out on the hood of the parts car with everything I think it needs to run, ignition switch, clutch switch, speedometer, ABS/BCM module, PCM, fuse block and PDC. All grounds were attached and grounded at the battery. The engine grounds are attached to the engine and is grounded to the battery.
Is the computer case grounded?
Is there something I missed or don't have hooked up properly?

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You say you've got it hooked to a '92 B250 fuel tank- is that the tank that was original to your engine? If not, that could be your problem.
'92 was an odd year, as the TBI LA318 was replaced by the 5.2 Magnum, but the TBI LA 360 was still being used and would not be replaced by the 5.9 Magnum until the following year in '93. Therefore, there were two different tank/pumps being used in '92 depending on which engine was ordered- the TBI system required about 14 1/2psi., while the Magnums with MPFI needed 55-60 lbs. IIRC. So, if you're trying to run your Magnum off of a TBI tank & pump, you won't have sufficient pressure for it to operate.
 
Yes, the tank came from a '92 B250. The van had a Magnum MPFI 5.2, which is also in my garage. I didn't get the '94 Dakota tank because of reasons.
 
Get a fuel pressure gauge and screw it to the fuel rail test port. (Napa auto zone etc) they are picky about fuel pressure. Fix the leaky regulator. I had to ground the jtec ecu (2001) on my test stand for it to be happy. If you have fuel pressure, and the ASD relay is powering injectors/coils AND the fuel sync hasn’t been messed up it will fire.
 
FYI you don’t need any of the auxiliary stuff (column, dash, etc) to run it, If you have the PDC. A remote ignition switch and a start button is all it takes. Or you can hit the easy button and go to the magnum swap group on Facebook and grab a stand alone harness from Kerry Kinser and be done. He makes nice harness’s for both od1 and 2.
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Professor Fate said:
You say you've got it hooked to a '92 B250 fuel tank- is that the tank that was original to your engine? If not, that could be your problem.
'92 was an odd year, as the TBI LA318 was replaced by the 5.2 Magnum, but the TBI LA 360 was still being used and would not be replaced by the 5.9 Magnum until the following year in '93. Therefore, there were two different tank/pumps being used in '92 depending on which engine was ordered- the TBI system required about 14 1/2psi., while the Magnums with MPFI needed 55-60 lbs. IIRC. So, if you're trying to run your Magnum off of a TBI tank & pump, you won't have sufficient pressure for it to operate.
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I swapped a 5.9 Magnum in the place of my ‘91 318 TBI motor in my Dakota and used the same pump and tank. I checked the part numbers and they interchanged. The pump doesn’t have the FPR on it so pressure is controlled at the rail or TBI, and adjusted accordingly.

There are issues though depending on what year PCM as they went to a returnless style system and had a FPR on the pump. My 5.9 PCM is from that era, so I just made sure the static pressure matched and left the vacuum hose disconnected so pressure was constant like the PCM expected.
 
TT5.9mag said:
Get a fuel pressure gauge and screw it to the fuel rail test port. (Napa auto zone etc) they are picky about fuel pressure. Fix the leaky regulator. I had to ground the jtec ecu (2001) on my test stand for it to be happy. If you have fuel pressure, and the ASD relay is powering injectors/coils AND the fuel sync hasn’t been messed up it will fire.
Click to expand...
Thanks for suggesting this. I was thinking along those lines, to see what the pressure actually is instead of guessing.
I have a spare regulator. And I tried pushing on of the grounds onto the PCM case with no change. It would be easy enough to ground it.
The fuel sync is adjusted by moving the distributor and confirming position through scanner/tuner, right? If so, the distributor has been moved.
 
TT5.9mag said:
FYI you don’t need any of the auxiliary stuff (column, dash, etc) to run it, If you have the PDC. A remote ignition switch and a start button is all it takes. Or you can hit the easy button and go to the magnum swap group on Facebook and grab a stand alone harness from Kerry Kinser and be done. He makes nice harness’s for both od1 and 2.
View attachment 1716191136
Click to expand...
Thanks for letting me know who builds them if I need to get it done. I understand wiring and schematics and feel like I can make it work.
I just happened to have everything and it was easier to hook it all up and try it, then opening up the harness and rewire it for the Dart. Don't want to induce variables while troubleshooting the no start condition.
 
tcanin00 said:
Thanks for letting me know who builds them if I need to get it done. I understand wiring and schematics and feel like I can make it work.
I just happened to have everything and it was easier to hook it all up and try it, then opening up the harness and rewire it for the Dart. Don't want to induce variables while troubleshooting the no start condition.
Click to expand...
With a factory wiring diagram it’s pretty easy to trace what the ignition switch does in the PDC. All you have to do is simulate that. I did it with a toggle switch to the ignition relay, and a start button on the starter relay. The entire “truck” side of my harness was clipped at the firewall connection. I had to add back the diagnostic plug but everything else was clipped. The whole “engine” side of the harness (with the ECU) is basically stand alone and operates perfectly independent of the rest of it. The only 2 codes I had were for a battery temp sensor, and evap.
 
DionR said:
I swapped a 5.9 Magnum in the place of my ‘91 318 TBI motor in my Dakota and used the same pump and tank. I checked the part numbers and they interchanged. The pump doesn’t have the FPR on it so pressure is controlled at the rail or TBI, and adjusted accordingly.

There are issues though depending on what year PCM as they went to a returnless style system and had a FPR on the pump. My 5.9 PCM is from that era, so I just made sure the static pressure matched and left the vacuum hose disconnected so pressure was constant like the PCM expected.
Click to expand...
You know, I didn't think about needing a different PCM for a return style or returnless fuel system. The Dakota was returnless and the van was return style. I have the PCM's from both.
I tried both since they're easy enough to swap. The only difference I noticed was the Dakota PCM made the upshift light come on with the key on. It was a 5 speed truck.

Something that might be related is that have the van's a518 automatic, flywheel, and crank position sensor on the motor now. The Dakota CPS plug would not fit into the connector. I spliced the van's connector on and the wires are the same colors. Do you think there's a problem with the CPS? Also, there was no tach movement while cranking.
 
TT5.9mag said:
With a factory wiring diagram it’s pretty easy to trace what the ignition switch does in the PDC. All you have to do is simulate that. I did it with a toggle switch to the ignition relay, and a start button on the starter relay. The entire “truck” side of my harness was clipped at the firewall connection. I had to add back the diagnostic plug but everything else was clipped. The whole “engine” side of the harness (with the ECU) is basically stand alone and operates perfectly independent of the rest of it. The only 2 codes I had were for a battery temp sensor, and evap.
Click to expand...
Once I get it to run, I'll start tracing wires and see where to connect my car's wiring. I want to keep the Dakota's intermittent wiper control and cruise control, but those aren't necessary until I get the engine in and running.
 
The returnless fuel system really wasn’t. They just mounted the regulator back at the pump. But since it wasn’t vacuum referenced I’m not sure if the ecu was different.
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TT5.9mag said:
The returnless fuel system really wasn’t. They just mounted the regulator back at the pump. But since it wasn’t vacuum referenced I’m not sure if the ecu was different.
View attachment 1716191152
Click to expand...
That is true, the computer doesn't control fuel pressure.
Now this is just a theory, but it might adjust the duty cycle of the injectors since there is not a continuous flow of fuel in the rail.
 
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TT5.9mag said:
The returnless fuel system really wasn’t. They just mounted the regulator back at the pump. But since it wasn’t vacuum referenced I’m not sure if the ecu was different.
View attachment 1716191152
Click to expand...

The only real difference is the “returnless” style expects a constant fuel pressure while the return style with a FPR on the rail had a variable pressure depending on the amount of vacuum. And the PCM‘s were tuned to match. So if you run a PCM that used a “returnless” style, just leave the vacuum disconnected from the FPR since the PCM is tuned to expect a constant pressure.

Plenty of people have mixed and matched while ignoring this and haven’t had huge issues. But I think they run better if you take it into account. Kind of like running larger injectors and not tuning for them, it can work but maybe not as well as it should.
 
Something else to keep in mind is the injectors. No idea if a ‘92 Dakota with a return style fuel system used a different sized injector than a ‘94 Dakota with a “returnless” system. I would look them up on RockAuto to check.

Not saying it is why the motor won’t start, just something to keep in mind.
 
We know almost nothing about what this thing is actually doing, or not doing.

tcanin00 said:
I would think everything is working right on that end since it's firing.
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When you say it is "firing" what does that mean to do you, what is it doing? Does it have spark at the spark pugs or not? Does it have injector pulse?


tcanin00 said:
Also, there was no tach movement while cranking.
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This usually indicates no crank sensor input and will also result in no fuel pump operation, no injector pulse, and no ignition spark at the spark plugs.


tcanin00 said:
The fuel sync is adjusted by moving the distributor and confirming position through scanner/tuner, right? If so, the distributor has been moved.
Click to expand...
Fuel sync can be way off and it will usually still start and run if everything else is working correctly. All this does is let the PCM know where cylinder number one is at so it knows the firing sequence of the injectors. If the distributor pickup coil (cam sync sensor) does not work at all or is unplugged it will cause a no start issue, but there is a test in the older service manuals to unplug the distributor and jump the sensor wire and ground wire together, on and off, and it will allow the engine to start.
 
DionR said:
Something else to keep in mind is the injectors. No idea if a ‘92 Dakota with a return style fuel system used a different sized injector than a ‘94 Dakota with a “returnless” system. I would look them up on RockAuto to check.

Not saying it is why the motor won’t start, just something to keep in mind.
Click to expand...
Great information about how the different PCM's handle the different fuel systems. I agree that it's important to keep matching parts and systems together, or at least tune for the differences.
 
Bobzilla said:
We know almost nothing about what this thing is actually doing, or not doing.


When you say it is "firing" what does that mean to do you, what is it doing? Does it have spark at the spark pugs or not? Does it have injector pulse?



This usually indicates no crank sensor input and will also result in no fuel pump operation, no injector pulse, and no ignition spark at the spark plugs.



Fuel sync can be way off and it will usually still start and run if everything else is working correctly. All this does is let the PCM know where cylinder number one is at so it knows the firing sequence of the injectors. If the distributor pickup coil (cam sync sensor) does not work at all or is unplugged it will cause a no start issue, but there is a test in the older service manuals to unplug the distributor and jump the sensor wire and ground wire together, on and off, and it will allow the engine to start.
Click to expand...
I hooked a timing light up to cylinder 1 to see if it would strobe. Not scientific, but it gave me an idea of what was going on.

Turns out that the tach doesn't work. More on that later.

I thought I read that it will run with the fuel sync being off. If I remember right, the later OBD II JTEC systems were more affected by fuel sync compared to OBD I.
 
Thanks again for the great responses! I got it running! It was a combination of problems with the fuel system.
First thing was to check for pressure.
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Well there's your problem, no fuel pressure.
I didn't have a spare pressure regulator like I thought. What I had was the Dakota's original returnless fuel rails. So I put those on, and rerouted the fuel lines into preset regulator and filter assembly. It came with the Classic Performance EFI conversion for A bodies. I know it's a GM part, I think for a C7 Corvette.

Still no pressure after changing the regulator. I assumed the van's gas tank would have a sump area and the gallon of gas would be enough for the pump to pick up. There is not a sump area and the gallon of gas was only a 1/4" deep. So plan 3c.

I put the van's pump and sending unit in a 2 gallon bucket and poured enough gas in for the pump to pick up. Cycled the switch on a few times and it built up pressure. Pumped up to 55 psi and held, so I cranked it and it fired up.
It runs very rich and didn't want to rev up, but I think it's because of the cobled together exhaust and the fuel sync being out. I'll post videos once I figure that out. For the time being, here's a picture of the rat's nest minus the steering column. For some I thought the screws on the ignition switch were not removable. They're torx with a pin in the center. Just needed a torx bit that has a hole in the middle.
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Also, the tach doesn't work. When I started messing with the van's gas tank it was pegged past 6K and wouldn't reset with cycling the switch.
 
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