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Floor gas pedal to start? Intermittent.

3K views 12 replies 6 participants last post by  luv2rock 
#1 ·
1989 5.0 GT Manual.

Advanced electrical is not my forte. :smile2:
Know this is a shot in the dark just hoping to find someone that has seen this before since it seems pretty specific. Can't find a troubleshooting list that has this symptom listed.

It always starts and drives. Sometimes when I turn the key and its cranking but I can tell it's not going to fire, while cranking I put the gas pedal to the floor and it starts right up. From what I understand it should not do this as flooring the pedal is supposed to kill the fuel injectors to clear a flood.

These facts could be related but I don't know for sure:
While a friend had his laptop connected could see that the TPS (throttle position), ECT (coolant temp), ACT (air temp) sensors are all losing their ground ONLY while the starter is cranking. All 3 sensors share the same ground, the "ref ground", MAP and EGR also use same ground. **Keep in mind it starts normally half-or-most of the time without flooring the pedal. While hot and cold.

Recent changes:
I replaced a bad ECT (coolant temp sensor) that fixed a no start when hot issue.
I replaced a dead old Ford performance mini starter that had power wire with a new SVE mini starter that has a trigger wire. That positive wire goes to the opposite side of the starter solenoid as the old starter.

Thanks,
 
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#3 ·
Last fall I had 24lb injectors replaced with 36lb injectors. Drove it only couple times. This spring I installed new distributor and coil while trouble shooting the hot start issue and also the starter died.

Im pretty sure it does this new issue hot and cold but not 100% sure. I've been doing nothing but troubleshooting it this year. Took me forever to figure out the bad ECT.

EDIT: I'm sure it does it, sometimes, when hot. Just not 100% sure it does it when cold. Will find that out soon.
 
#6 ·
CLEAR flood start requires the throttle to be wide open before key is turned on, not during

When you do it during, you are adding more air, not cutting fuel

Therefore you need more air, or less fuel or a combo

Fords do not use mafs calibrated to any injector size
 
#9 ·
Have you tried pulling codes??
http://sbftech.com/index.php/topic,2471.0.html

The eec ground at the fender apron runs to pin 40/60 at the ecu and the signal return ground for the sensors runs to pin 46 at the ecu.Pins 40/60/46 are all tied together on the ecu circuit board,so it seems like the sensors should always be grounded.Make sure the eec ground is tight/corrosion free and the two black plugs are also.If theres an issue with pin 46,codes are usually present for all of the sensors that share the black/
white signal return ground wire.I believe if the tps loses its ground (black/white wire) the tps will output wot voltage during crank down the signal (dk green/lt green) wire.This will also kill injector pulse too because the tps should be outputting a closed throttle voltage (.50-1.19) during crank and idle. Maybe the tps is acting up intermittently, working correctly at times and not correctly at other times.The code test should pop a tps code,if this is the case.
 
#10 ·
New info. I have to go by what my tuner tells me and what I can remember. Since I'm not paying anyone I have to keep it organized myself which is also a challenge.

New info:

He already tried changing the injector pulse width last time we were working on it and it made it worse.

So before cranking the ECT and ACT are temp 160 but when cranking they drop to 60. He thinks when the starter cranks and adds load, because they share the same ground, when cranking the temp drops to 60 and the TPS at some points volts drop to 1 or 0.

Something weird with the shared ground so we will check that.

You guys are definitely giving some good info tho , I never would have found myself, and helping me understand it better. Much appreciated.

Will keep this updated as I go. I don't want to burn this thread cause I think it will keep helping. I've been turning wrenches on my cars forever but stuff like this I cannot do myself so thanks!
 
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