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Old 06-06-2018, 09:24 PM   #1
custom1970
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'89 K1500 engine replacement help

New to this forum, but not to the site. My son has a 89 short bed 4x4. The old trans and 350 were worn out, so he wanted to replace both at same time. We found a rebuilt '75 4 bolt 350 with a turbo 350. After some trans and engine bracket mods we finally got everything installed last weekend. Went to try and start and the starter is not getting power.
Wanting to know if there's any safety or computer deals that needs to be deleted or bypassed? Acts like neutral safety, but it's on column so shouldn't be a factor.
Have power to key, coil, fuel pump.... Just not to starter.
My next step is to re check starter, but hoping we missed something else. There's tons of unhooked wires when you go from new school engine to old school....
Any help much appreciated.., thanks
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Old 06-06-2018, 09:27 PM   #2
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Re: '89 K1500 engine replacement help

Pic of new engine before we had everything connected... Also, we saw the engine start and run before we purchased it.Name:  image.jpg
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Old 06-06-2018, 10:00 PM   #3
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Re: '89 K1500 engine replacement help

First thing first check the signal wire at the starter, have someone turn the key and put a test light on the small side at the starter.

Also make sure all your grounds are hooked up. Engine to body, body to battery etc. If the motor is not grounded it won't crank either. I just threw a 91 motor in a 52 truck using a 80s column and it started so don't thinking mixing and matching this stuff matters
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Old 06-07-2018, 09:29 AM   #4
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Re: '89 K1500 engine replacement help

Yes, the first thing we're going to do is re-check the starter, if it ever stops raining!! If that's the problem it's an easy fix.
What we're afraid of is that there's some safety device that's preventing the switch from sending power to the starter. There several old connectors for the '89 harness/engine that no longer have a home... and are not plugged into anything.
And the grounds were a good call, but the old straps were cleaned and hooked up.

Thanks,
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Old 06-07-2018, 10:52 AM   #5
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Re: '89 K1500 engine replacement help

Why not use the TBI?
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Old 06-07-2018, 11:24 AM   #6
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Re: '89 K1500 engine replacement help

I can't think of anything else then the neutral safety switch, especially since your using the same column and truck that shouldn't have been messed with. Just find such wire is the signal wire going to the starter, if it has no power trace of back to see if it's cut or is unplugged
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Old 06-07-2018, 12:23 PM   #7
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Re: '89 K1500 engine replacement help

Exactly what we were thinking of following the wire up. Unfortunately, it's buried inside the harness and it's going to be a pain getting inside of that mess of wires and then getting everything back together so it looks clean. I know worse case, we run a new wire from ignition.

Was just wondering about the old engine control module. In wiring diagrams the ignition switch has a wire going directly to it. Thinking since it's MIA, maybe it's preventing the starter circuit from being completed? I do not know much about the newer engines. I'm used to a engine only needing air, gas and spark...

As to using the TBI, that would be way to small for this engine. It's pretty built, should be pushing close to 400hp. We have a big Holley dbl pumper on it.

Thanks,
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Old 06-07-2018, 01:41 PM   #8
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Don't forget the relay

Haven't seen a starter circuit in years that did NOT use a starter relay. Check the fuse box label for one. See if you have power at the pin 30 connector. You could also put a jumper from pin 30 to 87 and try the key.

You could also ohm the purple wire back to the relay socket (pin 87).
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Old 06-07-2018, 02:20 PM   #9
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Re: '89 K1500 engine replacement help

That's a good idea. Didn't think of using a jumper at the fuse panel!

Thanks!
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Old 06-07-2018, 09:40 PM   #10
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Re: '89 K1500 engine replacement help

I used TBI on a 406 I built, worked just fine....
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Old 06-08-2018, 08:29 AM   #11
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Re: '89 K1500 engine replacement help

Usually the pins are labeled on the side of the relay.
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Old 06-10-2018, 08:51 PM   #12
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Re: '89 K1500 engine replacement help

Update, starter decided to to take dump between engine changes... Changed starter and the thing fired up almost immediately.
New problem. It keeps running out of fuel. We are using the factory in tank fuel pump with a pressure regulator. When you turn key on pumps runs for 2-3 secs then shuts off. Will not kick back on until you re start the key.
Thinking something with the old harness is telling it to stop. I can wire pump to run off of the key, but do not know if that's the correct solution.
Looking for help and ideas, thanks
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Old 06-11-2018, 02:09 PM   #13
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Re: '89 K1500 engine replacement help

On the stock configuration there is an oil pressure switch that is part of the fuel pump relay circuit. I think Nascar vehicles used to run a similar circuit an maybe they still do. No oil pressure signal and the engine shuts down. It sounds like you have just enough gas in the fuel bowl of the carb to run the engine until it goes dry.
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Old 06-11-2018, 08:06 PM   #14
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Re: '89 K1500 engine replacement help

Think your right. I see the oil press/fuel pump sensor on the wiring diagram. Looks like it has and orange and grey wire. Think if I connect those together it'd fool the pump into running?
And yes, after the initial burst of gas to the carb it does run out of gas.
Thanks
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Old 06-13-2018, 10:49 AM   #15
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Re: '89 K1500 engine replacement help

Quote:
Originally Posted by custom1970 View Post
Think your right. I see the oil press/fuel pump sensor on the wiring diagram. Looks like it has and orange and grey wire. Think if I connect those together it'd fool the pump into running?
And yes, after the initial burst of gas to the carb it does run out of gas.
Thanks
Problem with fooling or bypassing the system is the potential for the pump to dump a continuous flow of fuel on a hot engine when a line or fitting leaks or is damaged in an accident.
Additionally should a needle and seat stick (never happens on a Holley right ) you will promptly fill your crankcase with fuel when the key is turned on.

Either install the required oil pressure sending unit to keep the system working as it was designed or install a mechanical pump.

If you go with a mechanical pump the in tank pump will have to come out as it will hinder flow once you get up to highway speed.
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Old 06-13-2018, 11:38 AM   #16
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Hold on there, more questions than answers

Quote:
Originally Posted by custom1970 View Post
When you turn key on pumps runs for 2-3 secs then shuts off. Will not kick back on until you re start the key.
Quote:
Originally Posted by custom1970 View Post
after the initial burst of gas to the carb it does run out of gas.
Thanks
There's a few problems with what you wrote here. First, the pump only comes on for a few seconds and then shuts off if you don't start the engine. In other words, if you simply go KOEO (key on engine off) that's what it does. Then when you crank it over, it fires up the pump again.

Second, unless someone replaced the TBI with a carb. it doesn't have a carb. Third, you wouldn't know if the fuel is shutting off going to a carb since it has a bowl. So that is further proof you are probably seeing fuel squirting from the injectors in a throttle body. Also a carb wouldn't show visible signs of fuel unless the accelerator pump were compressed.

So the question is, do you have an actual problem with the engine starting or continuing to run? Or are you just concerned because when you go KOEO, the pump runs for a few seconds and stops?
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Old 06-13-2018, 02:58 PM   #17
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Re: '89 K1500 engine replacement help

Thanks for both responses.
First we have a Holley dbl pump carb, not a TBI. Yes, when you turn key to on, (not start), the pump goes for a sec or two. Also, we did not hook back up the old oil switch (it was leaking), the wiring diagram shows exactly what Determined and Mr. Rich are saying. That the fuel pump does need oil pressure to run. The carb/engine is definitely running out of fuel. The longer you cycle the key, the longer it'll run, but it will still run out of gas pretty quickly.

If there's gas in the carb, she'll run. Going to install the factory oil switch and hopefully that'll solve the problem. Unfortunately, have to take it to the parts store and match it up, as the one they say it should have is not the one that was on the engine.

Also hoping the fuel pump relay and hot fuel module are on the firewall or dash. I do still have the old engine, just not sure what they look like if they're still on it.

Thanks,
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Old 06-13-2018, 04:43 PM   #18
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Re: '89 K1500 engine replacement help

The fuel pump relay will only stay applied if the ECM receives a distributor reference pulse. (Engine running / engine cranking).

If you are not using the distributor / ignition that was in the truck, the fuel relay will not stay applied.

The circuit going through the oil sender will supply power to the fuel pump once there is oil pressure, as others have stated.

The ECM is going to be setting multiple trouble codes so the check engine light will come on.
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Old 06-13-2018, 07:38 PM   #19
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Re: '89 K1500 engine replacement help

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The fuel pump relay will only stay applied if the ECM receives a distributor reference pulse. (Engine running / engine cranking).

If you are not using the distributor / ignition that was in the truck, the fuel relay will not stay applied.

The circuit going through the oil sender will supply power to the fuel pump once there is oil pressure, as others have stated.

The ECM is going to be setting multiple trouble codes so the check engine light will come on.
Ok, not good news. This is what I was afraid of from the start. Question, once we hook up a factory oil switch will the pump run with oil pressure and the ECM
just make engine light come on? Or will the lack of dist signal kill the pump?

We're not using original ignition. Wondering what our best options are. Replacing pump with new electric and delete existing pump. Or installing the original distributor? Or something else?
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Old 06-13-2018, 09:04 PM   #20
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Re: '89 K1500 engine replacement help

Quote:
Question, once we hook up a factory oil switch will the pump run with oil pressure and the ECM
just make engine light come on? Or will the lack of dist signal kill the pump?
The ECM will applied the fuel pump relay for 2 seconds when the key is turned on, and then it will go off.

The oil sender will only supply fuel pump voltage once the engine has oil pressure.

You could have trouble after you shut off a hot engine and the gas evaporates from the carb then you go to start it and the 2 seconds is not enough to get it started and have oil pressure.

Quote:
We're not using original ignition. Wondering what our best options are. Replacing pump with new electric and delete existing pump. Or installing the original distributor? Or something else?
The original distributor needs all the system inputs for the electronic spark timing to work correctly. It won't have what it needs.

People I know that have swapped in an older engine with a carburetor have used a mechanical fuel pump.
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Old 06-13-2018, 09:29 PM   #21
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Re: '89 K1500 engine replacement help

Sounds like the mechanical pump will probably be the way to go. Going to try the new oil press switch (which we need anyways) and see what happens. At least it might help us keep the project going until we have a chance to drop the tank and go mechanical. I do have a few old working pumps so the hardest part will be the time to do it....
Would be nice to get it running well enough to get to muffler shop.... Hard to tune on open headers....
Btw, we did install a temp mechical oil pump before first start, oil pressure was very strong.
Again, thanks for the help!
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Old 06-13-2018, 09:51 PM   #22
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Re: '89 K1500 engine replacement help

You're welcome!
If you use the electric pump that is in the tank the fuel pressure will be so high the carburetor won't hold it back unless you use a fuel pressure regulator.

You do not have to drop the tank. I know of several people that used a mechanical pump and it was able to draw fuel through the pump in the tank without the tank pump having power to it.
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Old 06-14-2018, 10:58 AM   #23
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Re: '89 K1500 engine replacement help

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You're welcome!
If you use the electric pump that is in the tank the fuel pressure will be so high the carburetor won't hold it back unless you use a fuel pressure regulator.

You do not have to drop the tank. I know of several people that used a mechanical pump and it was able to draw fuel through the pump in the tank without the tank pump having power to it.
We are using a fuel regulator. That would be great if we didn't have to drop tank. I know someone else mentioned that at high speed/volume that the old pump would restrict the flow.... good to here that it shouldn't be a problem

How would you suggest the best way to deactivate the existing pump? It don't see a fuse and hate to just cut the wire...

Thanks,
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Old 06-14-2018, 12:06 PM   #24
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Re: '89 K1500 engine replacement help

Elec Fuel pumps always have a relay. Pull it or the fuse which they also have. considering carburetors only need less than 10 pounds of fuel pressure, there will be next to no restriction from the old pump.
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Old 06-14-2018, 12:24 PM   #25
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Re: '89 K1500 engine replacement help

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