Another Vortec question?? I need assistance

[BarryB]

I recently swapped out a 305 for a 350 in a 98 1500. This is my first time I've ever messed with a vortec, so Its all new to me. I swapped the computer out from the donor truck. 99 GMC yukon. Everything plugged up.I set the distributor like I've read to set it. It will start but only run for a second, and shut off. I've done this several times, pump priming everytime it cranks over. Pushed in the schrader valve on the fuel lines I've got fuel. For the brief second it does run it sounds good. I've double checked all my connections. Everything is hooked up. Both motors ran before they were swapped, just the 305 sat for a few months before it was worked on. I actually drove the Yukon out the back of the junkyard so it could be positioned to be pulled. It should run.

So someone thats messed with Vortecs more than I have, I would appreciate greatly some feedback.

[BarryB]

I forgot to add, I replaced the lower intake gaskets, while I had it out and on the stand. I wouldn't think that would have and reason for it not to stay running.

[bwood]

I can't think of many things that would cause it to start then stall. One thing that comes to mind is a fuel issue or a poor electrical connection. Do you have the ability to test fuel pressure and read codes? Also check all of your grounds, there should be 5 on the engine:

(2) on the back of the pass side cyl hd-
-1 from the frame
-1 from the harness on the fire wall
(2) on the pass front of the engine
-1 from the battery
-1 from the harness that connects to the Crank sensor and power steering pump
(1) on the tstat housing from the harness on top of the engine

Also make sure you have a good battery, when I swapped engines last year my battery was low and caused starting issues at first. Also double check sensors, I've forget to plug the MAF back in a had it stall once with this truck and my wife's car will start then stall every time if it is unplugged. Here is a list of the top of my head of critical sensors:

MAF=Mass Airflow Sensor, in intake tube between throttle body and air filter
IAT=Inlet Air Temp Sensor, just before the MAF
CKSPS=Crankshaft Position Sensor, in lower pass side of timing cover
CMSPS=Camshaft Position Sensor, in dist
Knock Sensor=pass side, middle of block above pan rail
Oil Pressure Sensor=nest to dist in the block
CTS=Coolant Temp Sensor, in intake next to tstat
TPS=Throttle Pos Sensor, on driver side of Throttle Body
IAC=Idle Air Control, on driver side of Throttle Body
EGR Valve, at front of intake near A/C compressor
O2 Sensors=1 on each bank before cat and 1 behind cat ****see edit below****

Now not all of these will keep it from running but they may set a code. If dist was off but close you would get the MIL for P1345 "Camshaft/Crankshaft corrolation error", but the truck would run. Will it run if you hold the throttle a little, if so it might be the IAC's operation.

Edit: Just a note on the O2 Sensors. The 305's used 3 like listed above, but the 350's used 4 because they used two cats; 1 before each cat and 1 after. I have heard that the 305 Y pipe doesn't breathe well enough for a 350, but I have no first hand experience on this. I do know that if you run the ECM for the 350 and use the 3 O2's for the 305 (not 4) you will get a O2 code for the missing sensor. If after checking everything and still no go, swap back to the 305 ECM and see if it starts.

[BarryB]

All the grounds are connected I made sure of that. All the sensor are hooked up I even went over and double checked the fitment, everything was tight.

I'll try the computer swap, but will that cause the 5.7 not to run correctly? Seeing that the perimeters are meant for a 5.0L.
I'll swap the ECM and check back.

[bwood]

It should be fine for testing. Remember your truck was a 5.0 so the rest of the truck still is except for 45 new cubic inches, the only thing different is how long it pulses the injectors, so you may run a little lean. But you also said that the 5.7 came from a 4x4 so the 5.7 comp will also look for anything 4x4 related also. IF it works ok with the 5.0 comp, I would send it out for a custom tune for the 5.7 and sell the 5.7 comp to recover some of the tuning expense (you might even sell it to the tuner).

You know something else that just popped into my head is the torque converter, I wonder if they are the same between the 5.0/5.7? This wouldn't cause you current problem, but may raise the stall from what the 5.7 was which is not realy a bad thing I don't think.

If the 5.0 comp does the same thing, its time to test fuel pressure and get a meter out and start check voltages.

[BarryB]

I swapped the 5.0 ECM back in. The motor started and stayed running. I'm just curious of the driveablity of the 5.7 with a 5.0 ECM?
To answer Bwoods other question, I do not have anything to check codes. I need to get myself one. Is there a cheaper one that I can get. I don't use one enough to justify purchasing a more expensive code reader.

[bwood]

Also make sure that when you put the dist in, it was on TDC on the comp stroke and not the exhaust stroke.

I may have already posted this for you, but here is a thread with some pics of setting the dist:

http://67-72chevytrucks.com/vboard/s...ighlight=P1345

And here is a MS Word document on it also:
Distributor Installation SBC Vortec.doc

[BarryB]

Originally Posted by bwood

It should be fine for testing. Remember your truck was a 5.0 so the rest of the truck still is except for 45 new cubic inches, the only thing different is how long it pulses the injectors, so you may run a little lean. But you also said that the 5.7 came from a 4x4 so the 5.7 comp will also look for anything 4x4 related also. IF it works ok with the 5.0 comp, I would send it out for a custom tune for the 5.7 and sell the 5.7 comp to recover some of the tuning expense (you might even sell it to the tuner).

You know something else that just popped into my head is the torque converter, I wonder if they are the same between the 5.0/5.7? This wouldn't cause you current problem, but may raise the stall from what the 5.7 was which is not realy a bad thing I don't think.

If the 5.0 comp does the same thing, its time to test fuel pressure and get a meter out and start check voltages.

You beat me to the punch, this truck isn't going to be used all that much. basically to get materials from Lowes/HDepot or to take trash to the dump. basic light duty use. I'll have to check to see if I can find someone that can custom tune the 5.0 comp to the 5.7. If not do you think it would hurt just to leave it alone?

[BarryB]

Originally Posted by bwood

Also make sure that when you put the dist in, it was on TDC on the comp stroke and not the exhaust stroke.

I may have already posted this for you, but here is a thread with some pics of setting the dist:

http://67-72chevytrucks.com/vboard/s...ighlight=P1345

And here is a MS Word document on it also:
Attachment 484558

Yes it was set on the compression stroke. Actually it was that same thread I used to set the Dist.

[bwood]

I missed some of your posts, I think we posted around the same time. I can't see running with the 5.0 comp causing any issues, it will fuel less so you may only get warm 5.0 performance out of your 5.7. GM says that you can run there GMPP HT383E Vortec stroker in a orig 96-up 5.7 truck with no computer mods, so I don't think you will have any issues. You might call around/search though I don't think tuning it correctly will put you in the poor house especially if you can sell the other ECM and you old donor Yukon. I'm thinking under $300 for a basic tune.

[BarryB]

Heres the update, I put in the 5.0 Ecm. got it started and running. drove it around the block. unplugged the 5.0 ECM, plugged back in the 5.7 ECM, still wouldn't stay running. What the problem was. where I swapped the ECM's from different vehicles, the computer had to relearn the different security codes. After I reset the computer, it runs fine with 5.7 ECM
What I did was turn the motor over it started than shut off, left the key on for 10 minutes, turned it back off waited another 30 seconds. cranked it over. You have to do this three times to set the anti theft security codes. On the third try it started, stayed running and I've put 100 or more miles on it since then. stopped and started numerous times so it's good to go.

[BarryB]

bwood, I left you some rep points for heading me in the right direction.

[bwood]

Well good, I am glad to hear you got it running. I honestly forgot about the VATS. After youv'e run it for a while it might payoff to have the cam timing double checked, should be +/- 2 degrees from 0 @ 1000 rpm I believe. A shop with a Tech II scanner can do this for you and shouldn't charge you much if you don't have any engine lights. Did you swap the 5.7 y pipe in or did you keep the 5.0 pipe?

[BarryB]

Originally Posted by bwood

Well good, I am glad to hear you got it running. I honestly forgot about the VATS. After youv'e run it for a while it might payoff to have the cam timing double checked, should be +/- 2 degrees from 0 @ 1000 rpm I believe. A shop with a Tech II scanner can do this for you and shouldn't charge you much if you don't have any engine lights. Did you swap the 5.7 y pipe in or did you keep the 5.0 pipe?

I kept the 305 exhaust.Seems to run just fine, Like I said before or meant to say. It's not a DD truck, keeping it around just to have a truck if needed to haul the trash to the dump or get materials for house projects. You know its a truck and gets used as one.
OH I found out it has a Posi today. That puny 5.0 wouldn't even chirp the tires before. But it had seen better days though.

[bwood]

Cool, good to know. Thnx for the rep.