Should Lift Pump Run During Glow Cycle?

[joed]

On my 98 (manual trans.), it does.

On my dad's 95 (auto trans.), it doesn't run during the glow cycle. Is this normal?

The reason I ask is because my dad's truck is noticeably harder to cold start. We both have Kennedy's quick heat plugs, and his batteries are good.

I know his lift pump works as you can hear it when you shut the engine off due to the residual oil pressure, and the engine doesn't hesitate during hard acceleration.

Maybe it's the difference between auto and manual trans, or the difference of OBD 1 (1995) versus OBD 2 (1998) wiring?

If the lift pump isn't supposed to operate until cranking/running, could changing this be a factor in improving cold starting?

Any thoughts? Thanks. Joe.

[diesel65]

As you have found, the OBD 1 won't energize the pump until you crank the engine, then when you get oil pressure the oil pressure sensor will take over.
The OBD 2 system, the computer controls the fuel pump relay which then controls the fuel pump, the oil pressure switch serves as a backup if the relay should fail.

[Shad]

I am going through the same with my 94. I have found that if I crank the engine it doesent catch then I wait till I stop hearing the lift pump running then try again and she fires right up. It seems as though the lift pump needs to re-pressure the system. I wish my lift pump would start before I cranked the engine.

[joed]

Thanks for the info. That is what I suspected.

Given my lack of electrical/wiring understanding, would it be possible to run a lead from the wire that feeds the glow plug light on the dash to power the lift pump during glow? It would seem like it would work, but maybe the afterglow cycles after the engine started would be problem (the pump would be getting juice from 2 sources).

Granted this is not a huge deal, but if it could be wired without too much trouble it would probably be worth it.

Any thoughts? Joe.

[BUZZ]

yes you can power the lift pump from 2 deffernt potentials. YOu must install a blocking diode in to each potential to prevent reverse feeds.
I can check, but a IN 4001 diode should do the trick.
Buzz
http://www.diodes.com/datasheets/ds28002.pdf