Starting problem

[dave s]

My 94 with a 5.0 is only starting with a shot of starting fluid. New pump, filter. Bought truck new in 94, sold to my son in law in 06. Saw it sitting at his house two Christmas's ago, he said it wouldn't start. Couple months ago my daughter asked if I wanted it for free, I said sure! Had it shipped from Idaho to PA. It was just too rust free to not get back. I read and read while it was at tranny shop past two months(friend owns it, I said no rush) he did clutch and rebuilt the NV3500. I got CFM Technologies pieces to put gauge inline and check pressures. I got ahead of myself and put new Delphi pump in today. Still won't start until you give it a tiny shot of starting fluid, then runs perfect! I took tbi off and disassembled and cleaned it. Kit I got didn't have a new diaphragm for regulator or injector filter screens so I'll get them tomorrow. My question is where to go next? I read a lot about the pickup coil and module in distributor curing this issue as well as relays, oil pressure switches, thermostat temp sensor or something like that. When it runs it runs good! I tested the clutch with a nice posi burnout and a long pull up a mile long grade hammered down and no fuel starvation symptoms I could tell. Ran strong. Pulled in, shut off and tried to start, just turns over and when you let off key you can hear pump running for a few seconds and then it quits. I haven't tried it cold but before today, it didn't matter if cold or hot, no start without a shot. Any ideas where to start?

 

[texas tough]

let me ask you,, when you try to start it, are you pumping the pedal to the floor a few times? if you are, it will put the computer into a " clear flood mode" and wont pump fuel until certain parameters are met.. just crank it over, with very little throttle or no throttle and see what it does. sometimes folks forget, and think these trucks have an accellerator pump but they dont.

 

[texas tough]

the other scenario, is these trucks have 2 paths to engage the fuel pump,, thru a circuit in the oil pressure switch, and the fuel pump relay.. if the fuel pump relay isnt working the engine has to spin at 400 rmp or higher, then the switch will energize the pump.. so your fuel pump relay may not be working, and when you shoot some gas in, and it starts, the oil pressure switch lets it run.. Now as far as the fuel pump relay, its on the firewall under the plastic cover. theres a fuse in a holder next to it.. pull the fuse out and see if its popped.. if not , pull the harness out of the relay, and make sure the small pins arent corroded, and make sure the recieving pins in the harness are closed enough to make contact with the pins.. they can loosen over time and not make contact.. a small pick can be used to close the pin grabs some. everything needed to start the truck is in the distributor, that fuel pump relay, fuse, and pump. make sure the connectors that plug onto/ the top of the ignition coil are good too. when u turn the key to run position the fuel pump gets primed for 2 seconds, then shuts off, until you try to start it.. the pressure bleeds off immediately after truck is shut off. pressure shuld be 9 to 13 PSI.. also hopefully u didnt put a bigger spring in the regulator.. these trucks are VERY picky abt that spring. use an OEM or equal. theres people selling 14 to 18 psi springs that are causing alot of isuues with idleing and drivability. also the fuel pump relay can be bench tested with some alligator clip wires and a 12 volt battery.

 

[dave s]

let me ask you,, when you try to start it, are you pumping the pedal to the floor a few times? if you are, it will put the computer into a " clear flood mode" and wont pump fuel until certain parameters are met.. just crank it over, with very little throttle or no throttle and see what it does. sometimes folks forget, and think these trucks have an accellerator pump but they dont.

Nope, no pedal and I let it turn over a good while but not even a sputter. Then I jockeyed the pedal a bit but no go.

 

[dave s]

the other scenario, is these trucks have 2 paths to engage the fuel pump,, thru a circuit in the oil pressure switch, and the fuel pump relay.. if the fuel pump relay isnt working the engine has to spin at 400 rmp or higher, then the switch will energize the pump.. so your fuel pump relay may not be working, and when you shoot some gas in, and it starts, the oil pressure switch lets it run.. Now as far as the fuel pump relay, its on the firewall under the plastic cover. theres a fuse in a holder next to it.. pull the fuse out and see if its popped.. if not , pull the harness out of the relay, and make sure the small pins arent corroded, and make sure the recieving pins in the harness are closed enough to make contact with the pins.. they can loosen over time and not make contact.. a small pick can be used to close the pin grabs some. everything needed to start the truck is in the distributor, that fuel pump relay, fuse, and pump. make sure the connectors that plug onto/ the top of the ignition coil are good too. when u turn the key to run position the fuel pump gets primed for 2 seconds, then shuts off, until you try to start it.. the pressure bleeds off immediately after truck is shut off. pressure shuld be 9 to 13 PSI.. also hopefully u didnt put a bigger spring in the regulator.. these trucks are VERY picky abt that spring. use an OEM or equal. theres people selling 14 to 18 psi springs that are causing alot of isuues with idleing and drivability. also the fuel pump relay can be bench tested with some alligator clip wires and a 12 volt battery.

Ok, this is good info for me. I owned this truck when it was new and just drove it nice days. Only ever had to change fluids and rotate tires for 12 years. I think it had 23k when I sold it to them. My daily driver is an old square body step side chevy with a straght six and it's always easy for me to fix everything. I'm in uncharted waters now so to speak. As far as the tbi goes, it's still on the bench. I need a couple parts today and I'll finish it up and reinstall. I am using the spring I took out. Just need a new diaphragm that wasn't in the kit I got. I was reading all evening and sounds like a cable and program on my laptop would be handy to have as well. What's a good manual describing proper troubleshooting steps? I read guys all ohming things out, or checking voltages on tps's and stuff quoting specs. Is there a good book I could get? And thanks for the info, much appreciated.

 

[Crazydavez28]

While you're in there tweak the fuel pressure regulator. I did this to my Dad's 95 work truck that would start on hot days. Now it fires right up and gets all the fuel it needs.

 

[texas tough]

before u put the TB back on, get 2 containers and put the fuel pressure line in ne and return line in the other,. crank the truck over and see if u get fuel to the lines..

nothing in the throttle body makes fuel come too the TBI, it only regulates how much pressure it gets.. theres a myth going around that the TBI fuel pumps have a check valve in them to stop backflow of fuel, and that isnt correct.. it has an over pressure release vallve.

 

[texas tough]

the 94 does not have an adjustable fuel pressure regulator.. folks are putting big ass springs in them, thinking they are doing something , but on a stock motor, they are causing problems.

 

[Crazydavez28]

the 94 does not have an adjustable fuel pressure regulator.. folks are putting big ass springs in them, thinking they are doing something , but on a stock motor, they are causing problems.

The one I did was not adjustable I had to drill out the braze and turn it up to 15psi. About half a turn iirc

 

[texas tough]

sometimes the braze corrodes and deteriorates the solder deteriorates and lets the screw turn from vibrations,, this drove me nuts until I figured it out. if the pressure isnt between 9 and 14 psi, these trucks will not be happy.