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hard start after hot soak

5935 Views 14 Replies 8 Participants Last post by  greenfuel
I'm new to the site so I apologize if I'm asking a question that has already been answered.
I have a 1988 F-250 with the 7.3 IDI. It starts ok in the morning or any time it's cold but after it has been driven and then shut off for 30 minutes or so, it almost runs the batteries down getting started. Once it starts, it doesn't sputter or anything. It runs good. Anytime the "wait to start" light doesn't come on I know it's going to be hard to start. If the light does come on, it will start ok. When I say ok, it doesn't just jump to life but it starts after a few seconds of turning over. If I try to start immediately after shutting it off it starts right up quickly. So far I've had the lift pump, injector pump, glow plugs, control module, relay, injectors, return lines and caps and starter replaced. Should my "wait to start" light always come on when starting or just until it warms up enough? Could this be a lack of compression?
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First if the IP is new NEVER pour cold water on it.... sounds like air intrusion and fuel draining off should be checked first. Visit my gallery for the pic of the steel line seals. They could be part of the problem in they were not replaced. Then visit the page below for good air intrusion areas and the clear hose check........

There seems to be some confusion as to when the GPs are activated, below is the way they work on a 7.3.....

How ...The Solid State Circuit Works ........

This is 93 info, but other than the "maxi fuse" operation is same.

The Glow Plug Control circuit applies power to the Glow Plugs, which heat the combustion chambers so that the diesel engine can be started.

Glow Plug Controller
The solid-state Glow Plug Controller, attached to the top of the engine block, controls the Glow Plug pre-glow and after-glow time. It also controls the circuit's operation by sensing engine temperature, Glow Plug voltage and after-glow voltage from the start/run circuit.

When the Ignition Switch is turned to START or RUN, voltage from Maxi-fuse K is applied through the Glow Plug Controller to the Wait-To-Start Indicator Lamp.

The Glow Plugs heat up in zero to fifteen seconds, depending on engine coolant temperature. After the Glow Plugs heat up, the controller cycling switch opens and turns the Wait-To-Start Indicator Lamp off. The Glow Plugs are now warm enough for the engine to be started.

At the same time the Ignition Switch is turned to RUN, voltage from Maxi-fuse K is applied to the after-glow timer (located inside the Glow Plug Controller). The after-glow timer cycles the Glow Plugs for up to two minutes, depending on engine temperature. The after-glow timer then opens. The Wait-To-Start Indicator Lamp will not light during the after-glow period.

If the Ignition Switch is turned OFF, it can be turned to ON immediately, and the Glow Plug heating cycle will start again.

Diesel Start/Run
The diesel engine uses two batteries to provide extra power for starting and glow plug heating. Power is applied from the batteries, through heavy gauge wires, to the Starter Solenoid (located in the Starter Motor assembly). When the Wait-To-Start Indicator goes out, the Ignition Switch can be turned to START.

With the Ignition Switch in START or RUN, voltage is supplied to the Fuel Heater, Fuel Shutoff Solenoid, and the Engine Temperature Switch through Maxi-fuses K and U.

The Fuel Heater is in the Fuel Filter/Separator. It heats the diesel fuel, melting any wax that might clog the filter. The heater has an internal thermostat to turn it on as needed.

The Fuel Shutoff Solenoid controls the flow of fuel into the injection pump. With the Ignition Switch in START or RUN, the Solenoid is energized, and fuel is allowed to flow into the injection pump. When the Ignition Switch is turned off, the solenoid is deenergized, fuel flow stops, and the engine stops running.

The Engine Temperature Switch provides voltage to the Cold Timing Advance Solenoid and the Cold Idle Solenoid. When the engine temperature is below 112 °F (44 °C), the Engine Temperature Switch is closed. When the Ignition Switch is turned to START or RUN, the solenoids are energized, advancing injection pump timing and engine idle, allowing the engine to run more smoothly when cold. When the engine temperature reaches 112 °F (44 °C), the Engine Temperature Switch opens. This denergizes the solenoids, returning the timing and idle to normal.

To start turn key on press fuel pedal to the floor, then if above 30*F hold at 1/2 throttle, if below 30*F hold at 3/4-full throttle start engine. Once started release the fuel pedal to the fast idle setting or feather pedal to keep running.
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