Intermittent No Start

[VTRedSled]

So my '99 sat for a couple of months while I was saving up for new tires. I started it periodically and it always started without a problem. I got new tires about 4 weeks ago, When I went to pick it up from the tire place it would not start, It cranked fine but would not catch. I did not notice if the Tach was working. I went back about 20 minutes later with some tools to screw with it and it started right up. No problems again until about 1 week ago. It did not start in the middle of the day. The WTS light never came on. I let it sit about 5 minutes and it started right up. I replaced the cps the next day.

Yesterday it did the same thing. No WTS, no tach reading. I left it overnight and it started right up this morning. It has started fine all day today.

My #30 fuse is fine. The previous owner did tap into this fuse using half of a spade connector jammed in with the fuse. Unfortunately the fuse doesn't stay in without the connector jammed in there. I think I would have to bend the contact out to keep the fuse in place. I tried disconnecting the IPR and the engine won't start. I disconnected the IPC and it does start.

Is the new cps bad already? It's a grey on from Ford. I'm not sure what to try next, and I'm nervous about taking it too far from home. I know they are cheap but I'm frustrated at "throwing parts at it". I checked my oil and it was about 1/2 qt low, which I topped off. Thanks for any and all suggestions.

[woodnthings8]

Your batteries or starter are weak. Usaulally when you disconnect the ICP sensor you are providing a default reading to the pcm of something like 500 psi. If your starter is weak the hpop may not be getting the required psi to start.

Here is what is needed for a start:
7.3L Powerstroke Starting Req.:
Vehicle Power : 10.5v
RPM Signal : 100rpm
Inj. Cntrl Press. (ICP) : 0.85v (about 500psi)
Fuel Pulse Width : 1 to 6 milliseconds

[VTRedSled]

Originally Posted by woodnthings8

Your batteries or starter are weak. Usaulally when you disconnect the ICP sensor you are providing a default reading to the pcm of something like 500 psi. If your starter is weak the hpop may not be getting the required psi to start.

Here is what is needed for a start:
7.3L Powerstroke Starting Req.:
Vehicle Power : 10.5v
RPM Signal : 100rpm
Inj. Cntrl Press. (ICP) : 0.85v (about 500psi)
Fuel Pulse Width : 1 to 6 milliseconds

Starter seems to be cranking at a good speed. It starts up after 1-2 seconds.

[woodnthings8]

Originally Posted by VTRedSled

Starter seems to be cranking at a good speed. It starts up after 1-2 seconds.

The intermittent starting is what leads me to think you have weak starter or batteries. You could just barely be meeting the 500 psi pressure when you start. The truck will fire because it reads the minimums to start. When it doesn't start right up you could be just under the 500 psi range. The computer is fickle that way. After a bit of cranking that magic number is hit and she fires right up. Listening to the starter doesn't help much because it could litterly be a few rpm's difference causing this. The only way to really tell is hook up a computer to it and monitor those parameters previously listed. I have seen and heard of a quite a few trucks that have a newer starter and does the same thing, replace the starter and truck fires right up. Some put in the DB Starter which is a higher torque starter and that cures the problem. Diesels have lots of compression and require a good starter to get em going. Isolate your batteries and have them checked, you could have a weak one.

[VTRedSled]

Originally Posted by woodnthings8

The intermittent starting is what leads me to think you have weak starter or batteries. You could just barely be meeting the 500 psi pressure when you start. The truck will fire because it reads the minimums to start. When it doesn't start right up you could be just under the 500 psi range. The computer is fickle that way. After a bit of cranking that magic number is hit and she fires right up. Listening to the starter doesn't help much because it could litterly be a few rpm's difference causing this. The only way to really tell is hook up a computer to it and monitor those parameters previously listed. I have seen and heard of a quite a few trucks that have a newer starter and does the same thing, replace the starter and truck fires right up. Some put in the DB Starter which is a higher torque starter and that cures the problem. Diesels have lots of compression and require a good starter to get em going. Isolate your batteries and have them checked, you could have a weak one.

Would a repair shop or a dealer scanner measure these, or do you need a special program like autoengenuity? The last two times it seemed like a correlation between no WTS light and no start. I'll check the batteries, connections and the starter. Thanks for the suggestions.

[woodnthings8]

I would assume a repair shop that has a scanner would be able to access the needed sensor values, AE will definetely do it.

Something else you can check is the Glow Plug Relay. It could be causing your problem although this time of year not likely. Can you here it click on and off with the key?

The first thing to test on the system is the glow plug relay. This relay is a common point of failure. The glow plug relay is located on top of the engine right behind the fuel filter housing and slightly to the passenger side. If there are two relays located there it will be the relay toward the back of the vehicle with large yellow and brown wires leading to and from it. To test the relay you want to check the voltage at both large terminal posts right after turning on the truck. The glow plug relay should activate for 10 seconds or more, no matter what the temperature, longer when it is colder. You might wish to have someone turn the key to start while you have the meter on the terminals. Place the ground probe on a bare piece of metal somewhere on the engine and the source probe on each terminal. Both terminals should read around 12 volts. If one reads that and the other reads zero, you next want to check if the control module is bad or if it is the relay itself. (It most likely will be the relay. To test directly for function of the relay and make sure the problem isn't the control module you will need to apply battery voltage across the two small terminals on the top of the relay. At this point, if the relay is good, you should have 12 volts across both terminals. If the relay fails both of these tests you will have to replace the glow plug relay.

[woodnthings8]

Also try using this Hard/No Start? Check here first. for troubleshooting, as it is a great resource from the FAQ section