V8 Swap, No Start

[Broosedamoose]

Got my V8 installed and hooked up. Programmed with PATS disabled. The first time I turn the key after loading the program it will fire up for just a second and then quit. After that it just cranks and won't do anything. If I return the truck to stock and reload the program it will do exactly the same thing! Anyone run into this or know what it might be?

 

[RonD]

So its a 2003 Ranger with (what year) 5.0l and computer

Have you tried 50/50 test
See if you can keep it running by squirting fuel into the intake after startup
This would tell you if it is lack of Spark or lack of fuel thats causing the shut down


Fuel pump only runs for 2 seconds with key on, then doesn't come on again until RPMs are above 400

After the start/shut down cycle the key off/on and see if you hear the fuel pump for that 2 seconds, and if it restarts, maybe computer is not restarting the fuel pump after initial startup


Make sure crank sensor looks OK and its wiring, this is the main engine/computer sensor and about the only sensor that can cause a no start

 

[Broosedamoose]

It's a 1999 Explorer engine and PCM. What's a 50/50 test?

 

[Ramcharger90]

That crank sensor is a good place to start a wire could be exposed causing it to arc and or ground out. I had to fix this on a 4.0 exploder before. Check your grounds. Also grab a soda bottle poke a hole in the cap fill with gas and spray it in the intake while cranking if it wont stay running after that bang on the tank you might need a fuel pump.

 

[RonD]

50/50 test
Spray gasoline or ether into the intake
Try to start engine

If it starts and dies you have spark but no fuel
If it doesn't start you have no spark
50/50 instant diagnoses

In your case you use it to see if spark is shutting off or fuel is, after initial start up

 

[Broosedamoose]

Does anything other than the PATS disable the engine? i.e. factory alarm I'm pretty sure it's just PATS. It's just odd that when I return the truck to the stock calibration and then reload the tune it will try to start just the one time and then it will just crank after that and do nothing. I know it's not PATS because it's disabled within the tune and the Theft light does not flash while cranking. Now if I return it to stock and try to start it the Theft light flashes because PATS is enabled in the stock calibration.

 

[RonD]

Yes, odd, it reads like PATS may not be fully disabled, PATS light is disabled, lol

1999 Explorer had Type B PATS so a separate PATS Module above Glove Box, and NO starter interrupt, so engine would turn over regardless of PATS status

So PATS in 1999 controlled injectors and fuel pump only

Do you HEAR the fuel pump come on each time key is turned on??
Or just the first time?

Maybe injectors are activated but not fuel pump, so start up, use up fuel pressure and die

Computer needs an "OK to Start" message from PATS module with Type B PATS, but if PATS software in the computer is erased it wouldn't needed it, 1996 or 97 Explorer V8 computer didn't have PATS test

 

[Broosedamoose]

I double checked and PATS is definitely disabled. When I load the tune to the PCM, the first attempt to start I hear the fuel pump run and the engine just fires up and quickly dies. After that, when I turn the key I hear no fuel pump. So I am assuming that there is something else other than PATS controlling the fuel pump. I'm going to try swapping the PATS modules, reprogramming everything and see what happens.

 

[RonD]

If you hear the fuel pump the first time then fuel pump fuse, FP relay and inertia switch are OK

The PATS module Grounds the Starter Motor relay

The Computer Grounds the FP relay and Fuel injectors
So it reads like key on gets the initial 2 second Ground for FP relay, but computer doesn't ground it again once engine RPMs are above 400, which it should.

Do a few key on and off but don't start engine, see if Fuel pump runs each time

Pin 80 on computer, light blue/orange stripe wire, is the ground for the FP relay

You could ground that wire, use a sewing needle to pierce it and ground needle
Or pull out the FP relay and install a jumper so fuel pump is on all the time
Then see if engine stays running, so fuel injectors are working, just not the Fuel Pump circuit

If engine still stalls then it is PATS related because it disables BOTH FP relay and injectors

 

[Broosedamoose]

The fuel pump will only run the first time I turn the key on after uploading the tune. After that initial run, nothing happens. Now is it possible, since my truck does not have a PATS module (PATS E uses the PCM directly) and therefore nothing is connected to the wire going into the PCM coming from the PATS module it's not seeing the "ok to run"? I'm wondering if disabling the PATS only disables the key and transceiver but the PATS module still send an "ok to run" signal to the PCM. Starting to wish I had gone carbureted!

 

[Broosedamoose]

Does anyone know which wires I need to connect the PATS module to the PCM. Since my truck has a type-E system there will be no harness to plug the module into! Or, is it feasible to get the entire harness out from the module to the main connector at the firewall?

 

[RonD]

It wouldn't run first time if it was PATS issue, as far as I know

If you disabled only the key or transceiver then you would have a PATS problem

Here's the PATS module wiring

 

[Broosedamoose]

OK, the fuel pump is running each time the key is turned on so that much is good. Still no start though. He said he checked the injectors with lights and they were all working ok. He is going to check them again to see if they are getting pulsed as they should. He is confident there is spark so it should start! It has to be an issue with the injectors! I'm using the red Ford Racing injectors, but that shouldn't prevent it from running.

 

[RonD]

If it starts by adding fuel manually, then spark and spark timing is OK

"Ford Racing injectors" should still use 11-18ohms(high impedance), but double check to be sure, look up the specs for the model number

Unplug TPS then try to start
If TPS sends computer 4.5volts then it will disable injectors during cranking, its called Clear Flooded Engine routine

 

[2Krngr]

I would put a fuel pressure gauge on the schrader valve on the fuel rail. This will 100% let you see what is happening with the fuel.

You say it starts one time. But what does it do? Can you drive it around just fine until shut-off, or does it run for a bit and die?