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Help With Ongoing Project

Upstate

Upstate

1/2 ton status
- In Memoriam -
Joined
Aug 16, 2010
Posts
951
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Location
New York
Earlier this year (Spring) I got this brilliant idea. My daughter needed a vehicle and she loves to hunt / fish and we live in the snow belt (220"+ average) so why not a K5. I knew where this was one at a decent deal that I actually owned in the mid 90's.

So, me being the Dad that I am wanted her to learn about the vehicle she was going to drive so we decided to make it a project that we could do together.

The project is 1984 K5 that needed the transmission rebuilt and had serious issue with the electrical and at the time the motor did not run. It also had some rust but not bad. So we bought it.

In the mean time I was looking at parts trucks for the electrical etc. I came across a 1987 K5 which was sold as having a rebuilt short block with timing issues but had a almost perfect southern body other than the really bad paint fade. Rust free bodies in upstate New York are not to be taken lightly. In short, a '87 K5 rust is almost unheard of.

So now we have a '84 and '87. I decide to get the '87 running. Did not work out the way I planned. The rebuilt short block was rebuilt but soon after being rebuilt it was seized (before I bought it). You name it, some part of everything was f-ed in one way or another.

So, now I have a '79 350 motor in the '87 with the factory TBI intake drilled out to fit the older heads and tried to get the truck running. It will start with pouring gas in the TBI, but nothing else. Fuel pump works, distributor works in another truck I have so ICM, etc is a non issue. I work 65 hours a week and my kid needs a vehicle to go back and forth to school and work with, so I need to get this running.

I would like to use the electric fuel pump that is in the tank, put a regulator on it and go back to carb for right now till I get time to sort all of the TBI issues. Does anyone see any reason why this can't be done.

I do have the mechanical fuel pump also if I can just siphon through the electric pump (in the tank instead) so that way I don't need to buy a regulator.

I already have a performer intake and Edelbrock electric choke carb to sit right on top.

Thoughts?
 
Bad oil pressure switch? Not sure on the exact details but I believe there is a pressure switch that needs to see oil pressure before sending power to the fuel pump or something to that effect. Was that swapped over from the TBI engine to the older engine? Maybe the older engine isn't getting good oil pressure till it's running? Bad/weak fuel pump providing enough flow to run but not get started? Bad power/ground at the fuel pump? You need to start doing some diagnostic work.

Just throwing ideas out there. I'd do everything I could to keep the TBI on there. Changing over to carb is like stepping backwards, almost adding new problems rather than just fixing what you have. The TBI system is simple and reliable in all sorts of conditions.

If you have to change it over.... The TBI fuel pump is about perfect pressure to run a carb without a regulator. Although, if your problem is a bad/weak pump changing it over to carb wont change anything.
 
496truck said:
Bad oil pressure switch? Not sure on the exact details but I believe there is a pressure switch that needs to see oil pressure before sending power to the fuel pump or something to that effect. Was that swapped over from the TBI engine to the older engine? Maybe the older engine isn't getting good oil pressure till it's running? Bad/weak fuel pump providing enough flow to run but not get started? Bad power/ground at the fuel pump? You need to start doing some diagnostic work.

Just throwing ideas out there. I'd do everything I could to keep the TBI on there. Changing over to carb is like stepping backwards, almost adding new problems rather than just fixing what you have. The TBI system is simple and reliable in all sorts of conditions.

If you have to change it over.... The TBI fuel pump is about perfect pressure to run a carb without a regulator. Although, if your problem is a bad/weak pump changing it over to carb wont change anything.
Click to expand...

Yes, it is a older motor with very solid oil pressure.

Electric fuel pump is good. I could be wrong, but '87 should be in the teens for psi while the carb should be in the 6-9 range.

I understand your point of backwards, but this truck has been anything but a pia. I don't even know what issues I will have with TBI or the ECM. Oil pressure is a solid 40 psi at idle based on the gauge I had while it was carbed.
 
Prob not oil press then.

It starts with fuel added. Are the injectors delivering while cranking?
 
496truck said:
Prob not oil press then.

It starts with fuel added. Are the injectors delivering while cranking?
Click to expand...

No. It is definetly sensor or ECM related. When I bypass the relay the pump works and it pumps right to the TBI. But they will not fire
 
Injectors need a crank signal to fire. Crank signal comes from the ignition module in the distributor.

You've put a finger under the injectors while cranking? Made sure they are spitting out fuel or not?

You can do whatever you want. I just hate to think it's some stupid little issue preventing the TBI from working properly.
 
496truck said:
Injectors need a crank signal to fire. Crank signal comes from the ignition module in the distributor.

You've put a finger under the injectors while cranking? Made sure they are spitting out fuel or not?

You can do whatever you want. I just hate to think it's some stupid little issue preventing the TBI from working properly.
Click to expand...

Injectors are dry. I pulled another distributor from a running driving truck of the neighbors. Before doing that I replaced the ICM in our dist. No luck either way.

I hear what you are saying about it is a stupid idea. Issue is I need a vehicle for her and I am out of ideas on what is wrong with the truck.

Beyond that I have 20 other projects that are equally important plus my job. I am at the breaking point. I someone has any other ideas I am all ears to other ideas.
 
I just went through and rechecked all grounds. :dunno:

Anyone have any luck with Holley's Projection? I can go back to the Edelbrock manifold and Holleys TBI.

Thoughts?
 
Fuel pressure? Does it have any?

Injector pulse? Or even power to the injectors? Power to them while cranking?

If you are getting spark then the problem is with the fuel side. Start doing some tests and checks. I still think it's something simple keeping this thing from working. All the fusible links down at the starter good?
 
496truck said:
Fuel pressure? Does it have any?

Injector pulse? Or even power to the injectors? Power to them while cranking?

If you are getting spark then the problem is with the fuel side. Start doing some tests and checks. I still think it's something simple keeping this thing from working. All the fusible links down at the starter good?
Click to expand...

Fuel pump works, but only when bypassed the relay. Still don't start when bypassed though.
 
Sounds like a neat project to do. I have no tbi input, but why take a rust free southern truck to be used as a winter truck? Kinda defeats the purpose of owning a rust free body that the salts just gonna destroy anyways. Id save the rusted 84 for winter. Just my opinion though.
 
Upstate said:
Fuel pump works, but only when bypassed the relay. Still don't start when bypassed though.
Click to expand...

OK, so, it might have some sort of fuel pressure. You said it ran with some starting fluid so we can assume it has proper pressure. But, you know what happens when we assume.

How 'bout the other things I mentioned? The fact that you have to bypass the FP relay is a clue. There must be an incomplete circuit somewhere. Something isn't operating the relay. Start with fuses, they are easy. Don't try to figure out which fuse does what, pull every one out, one at a time, and inspect. You could also use the test light method if you don't feel like laying under the dash RnRing fuses. Also, as I mentioned, power at the injectors? Power at them while cranking? Injector pulse while cranking (is the ECM grounding them out or "pulsing" them while cranking)?
 
496truck said:
OK, so, it might have some sort of fuel pressure. You said it ran with some starting fluid so we can assume it has proper pressure. But, you know what happens when we assume.

How 'bout the other things I mentioned? The fact that you have to bypass the FP relay is a clue. There must be an incomplete circuit somewhere. Something isn't operating the relay. Start with fuses, they are easy. Don't try to figure out which fuse does what, pull every one out, one at a time, and inspect. You could also use the test light method if you don't feel like laying under the dash RnRing fuses. Also, as I mentioned, power at the injectors? Power at them while cranking? Injector pulse while cranking (is the ECM grounding them out or "pulsing" them while cranking)?
Click to expand...

There is no doubt that there is a electrical issue in the since I can bypass the fuel pump and make it work. It is in my mind a issue with the ECM.
 
If the plugs are firing then the module in the distributor is working, so the injectors should also be firing.
The injectors fire off of a switched ground on the TBI trucks, so one leg (wire) should have +12Vdc on it all the time when the key is on. Check that first. If you have the +12Vdc then re-check all of your grounds.

I have the Helm manuals with all of the troubleshooting info it it, but I don't have a scanner. I could take pictures of the pages and e-mail them to you if you need
 
readymix said:
If the plugs are firing then the module in the distributor is working, so the injectors should also be firing.
The injectors fire off of a switched ground on the TBI trucks, so one leg (wire) should have +12Vdc on it all the time when the key is on. Check that first. If you have the +12Vdc then re-check all of your grounds.

I have the Helm manuals with all of the troubleshooting info it it, but I don't have a scanner. I could take pictures of the pages and e-mail them to you if you need
Click to expand...

No power to the injectors.
 
Wires 467(lt blue) and 468(lt green) come from the ECM to switch the grounds. Looks like pins D16 and D14
Wires 481(red) and 482(white) get power from the battery, through the ignition switch and through the INJ. A fuse.

I have a injector troubleshooting section here we could walk through if needed.
 
readymix said:
Wires 467(lt blue) and 468(lt green) come from the ECM to switch the grounds. Looks like pins D16 and D14
Wires 481(red) and 482(white) get power from the battery, through the ignition switch and through the INJ. A fuse.

I have a injector troubleshooting section here we could walk through if needed.
Click to expand...

I am open for ideas.
 
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