No wait to start light

[JKellis]

Most of the time my truck starts just as it should. Occasionally when I turn the key the wait to start light does not come on. When this happens the engine turns over, but will not start, as if the VP is not getting a signal to fuel. If I turn the key to off and wait a few seconds, the wait to start light works and the truck starts like normal. It doesn't seem to matter if the engine is cold or warmed up. I am worried that my PCM is going. Wondering if anyone else has had this problem. Thanks

 

[JKellis]

Most of the time my truck starts just as it should. Occasionally when I turn the key the wait to start light does not come on. When this happens the engine turns over, but will not start, as if the VP is not getting a signal to fuel. If I turn the key to off and wait a few seconds, the wait to start light works and the truck starts like normal. It doesn't seem to matter if the engine is cold or warmed up. I am worried that my PCM is going. Wondering if anyone else has had this problem. Thanks

Anybody?

 

[DavidC]

Your sensor and wiring along with the light involves the ECM, not the PCM. I would start at the sensor wiring connector and if the wiring and plug check ok throw a new intake air temperature sensor in it. I would also try disconnecting the batteries and let it sit about 8hrs. Sometimes the electronics get a hiccup. There is a large electrical plug (C125) on the drivers side of the firewall that you may want to inspect also. It is between the valve cover and brake cylinder.

 

[JKellis]

Your sensor and wiring along with the light involves the ECM, not the PCM. I would start at the sensor wiring connector and if the wiring and plug check ok throw a new intake air temperature sensor in it. I would also try disconnecting the batteries and let it sit about 8hrs. Sometimes the electronics get a hiccup. There is a large electrical plug (C125) on the drivers side of the firewall that you may want to inspect also. It is between the valve cover and brake cylinder.
View attachment 126069

Thanks, but the problem is not with the grid heaters,. when the engine is warmed up it should start without the grid heater working, but it doesn't. When I turn the key to the on position and don't see wait to start, the VP will not pump fuel to the injectors. If I turn the key off and wait a few seconds everything works fine and the truck starts right up. Pretty much with a bump of the key. It's like if the ECM doesn't activate the grid heaters, it also failed to activate the VP.

 

[JKellis]

Thanks, but the problem is not with the grid heaters,. when the engine is warmed up it should start without the grid heater working, but it doesn't. When I turn the key to the on position and don't see wait to start, the VP will not pump fuel to the injectors. If I turn the key off and wait a few seconds everything works fine and the truck starts right up. Pretty much with a bump of the key. It's like if the ECM doesn't activate the grid heaters, it also failed to activate the VP.

I will go ahead and inspect, clean, and put some dielectric grease on all my connections, maybe I'll get lucky. Thanks

 

[DavidC]

Thanks, but the problem is not with the grid heaters,. when the engine is warmed up it should start without the grid heater working, but it doesn't. When I turn the key to the on position and don't see wait to start, the VP will not pump fuel to the injectors. If I turn the key off and wait a few seconds everything works fine and the truck starts right up. Pretty much with a bump of the key. It's like if the ECM doesn't activate the grid heaters, it also failed to activate the VP.

FYI, I never refrenced the grid heaters. Everything was for the IAT, wait to start light and ECM. The IAT tells the ECM it's cold and it turns on the wait to start light or the wait to start lights when doing the bulb check after turning on the key. I mentioned that plug as there are a few 12vdc supplies to the ECM and vp wires.

 

[JKellis]

FYI, I never refrenced the grid heaters. Everything was for the IAT, wait to start light and ECM. The IAT tells the ECM it's cold and it turns on the wait to start light or the wait to start lights when doing the bulb check after turning on the key. I mentioned that plug as there are a few 12vdc supplies to the ECM and vp wires.

Thanks David, guess I misunderstood. It's going to warm up here this week so I plan to get out and work on it. What is so weird to me is that it only happens every fourth or fifth time I start the truck. Doesn't seem to matter if it is cold or warmed up. Turning off the key and turning back on corrects the problem every time(so far).

 

[DavidC]

Thanks David, guess I misunderstood. It's going to warm up here this week so I plan to get out and work on it. What is so weird to me is that it only happens every fourth or fifth time I start the truck. Doesn't seem to matter if it is cold or warmed up. Turning off the key and turning back on corrects the problem every time(so far).

That's what makes it sound like an intermittent connection problem and hard to diagnose. It could be anything from the Ignition switch, a connection problem at a plug, a wiring problem and all the way to the ECM (Heaven forbid). Be ready as it could take a while to find. If it happened constantly it may be easier to find. It could be as easy as the IAT being flaky. What bothers me is the no start as many do not wait on the light which maybe the ECM not getting one of the 12vdc supplies or the ECM. But you would need to check as much as you can before going into the dollar and ECM grief first. I do not believe in throwing parts and money at things but this one is cheap enough if you do not find anything with plugs and wiring and is just the price to pay along the road.
https://www.genosgarage.com/product/sensor-3408345/electrical-sensors-2

 

[hcole]

JKellis, look at this old post about your problem. It speaks for itself. https://www.turbodieselregister.com/threads/ecm-lift-pump-relay-install.250467/#post-2420249

 

[petersonj]

@DavidC is pointing you in the right direction. From what I understand the illumination of the "Wait to Start" light is done by the ECM. That is why the "Wait to Start" light always lights regardless of conditions when the ignition switch is turned to "Run". If the light does not light briefly, then the ECM did not send the output because of possible wiring problems, missing an input command, or a faulty ECM. When the "Wait to Start" light does not illuminate, there will be no fuel command to the VP44, consequently a no-start condtion. Here is a list of ECM inputs and outputs from my 2002 FSM.

You may want to get a good code reader and check for any codes.

NOTE: ECM Inputs:
† Accelerator Pedal Position Sensor (APPS) Volts
† APPS Idle Validation Switches #1 and #2
† Battery voltage
† Camshaft Position Sensor (CMP)
† CCD bus (+) circuits
† CCD bus (-) circuits
† Crankshaft Position Sensor (CKP)
† Data link connection for DRB scan tool
† (FPCM) Fuel Injection Pump Control Module
† Engine Coolant Temperature (ECT) sensor
† Ground circuits
† Intake manifold Air Temperature (IAT) sensor
† Manifold Air Pressure Sensor (Boost Pressure
Sensor)
† Oil pressure sensor
† PCM
† Power Take Off (PTO)
† Power ground
† Sensor return
† Signal ground
† Water-In-Fuel (WIF) sensor

Outputs. These outputs are for:
† CCD bus (+) circuits
† CCD bus (-) circuits
† CKP and APPS outputs to the PCM
† Data link connection for DRB scan tool
† Five volt sensor supply
† Fuel injection pump
† Fuel injection pump relay
† (FPCM) Fuel Pump Control Module
† Fuel transfer (lift) pump
† Intake manifold air heater relays #1 and #2 control
circuits
† Malfunction indicator lamp (Check engine lamp)
† Oil pressure gauge/warning lamp
† PCM
† Wait-to-start warning lamp
† Water-In-Fuel (WIF) warning lamp

- John

 

[Joe Mc]

There is a large electrical plug (C125) on the drivers side of the firewall that you may want to inspect also. It is between the valve cover and brake cylinder.
View attachment 126069

Careful when you unplug these two that you don't break any of the "too close for comfort" fragile plastic vacuum lines that control heat & air registers as well as, if you break and don't realize, cruise... you don't have to ask how I know this, right LOL...