losin power to inertia switch
#1
09-21-2016, 12:57 PM
Join Date: Sep 2016
Location: pine city washington
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losin power to inertia switch
i am working on my friends 95 f-150 with a 351 engine and duel tanks. he got the truck for free it was driven to california and back from cour de alene twice then parked last winter. there is 3/4 of a tank in the front and 1/2 in the back. you turn the key on and it builds pressure for a few seconds like it is suppose to not sure how much (no gauge yet) but when you crank it no start. it had a weak yellow spark so i changed the coil now it has a strong spark,still no start but,if i spray starting fluid in the air inlet tubes it will fire for a few seconds. i have checked all the fuses and relays,the horn works so i substituted the horn rely for the fp relay still nothing, and no power to either pumps,so i took off the inertia switch it wasn't tripped and had continuity but no power with the key on or off. when i turn the key on i have power to the f p relay but none to the inertia switch,if i run power to the inertia switch then i get power to the pumps but they still won't kick over so i'm thinking between thefuel pump relay and the inertia sw is a broken wire. there is a connection called c202 according to the shop manual i saw at the library it also mentioned the fuel system computer where is that? sorry about the ramblings this truck has me dazed and confused checked the select switch it is working as well and it is a 2 hr trip to fix this truck.
#2
09-21-2016, 04:51 PM
Since you're getting the 3 second prime the fuel pump circuit is working fine
Turn the key one click and the PCM/computer turns the pump on for 3 seconds and times out
Turn the key to start, the PCM sees ignition pulses and orders the pump to run again.
If the pump is'nt running while the engine is cranking, pull the codes and see if they give you any clues.
I think there is a code for lack of ignition pulses or some such. Thats about all i can tell you.
If this uses a crank sensor that would be suspect.
Turn the key one click and the PCM/computer turns the pump on for 3 seconds and times out
Turn the key to start, the PCM sees ignition pulses and orders the pump to run again.
If the pump is'nt running while the engine is cranking, pull the codes and see if they give you any clues.
I think there is a code for lack of ignition pulses or some such. Thats about all i can tell you.
If this uses a crank sensor that would be suspect.
#3
08-09-2021, 07:50 AM
i am working on my friends 95 f-150 with a 351 engine and duel tanks. he got the truck for free it was driven to california and back from cour de alene twice then parked last winter. there is 3/4 of a tank in the front and 1/2 in the back. you turn the key on and it builds pressure for a few seconds like it is suppose to not sure how much (no gauge yet) but when you crank it no start. it had a weak yellow spark so i changed the coil now it has a strong spark,still no start but,if i spray starting fluid in the air inlet tubes it will fire for a few seconds. i have checked all the fuses and relays,the horn works so i substituted the horn rely for the fp relay still nothing, and no power to either pumps,so i took off the inertia switch it wasn't tripped and had continuity but no power with the key on or off. when i turn the key on i have power to the f p relay but none to the inertia switch,if i run power to the inertia switch then i get power to the pumps but they still won't kick over so i'm thinking between thefuel pump relay and the inertia sw is a broken wire. there is a connection called c202 according to the shop manual i saw at the library it also mentioned the fuel system computer where is that? sorry about the ramblings this truck has me dazed and confused checked the select switch it is working as well and it is a 2 hr trip to fix this truck.
Soo almost 5 years later.. curious minds with similar problems are wondering did you ever figure out what it was??
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5oh95
1987 - 1996 F150 & Larger F-Series Trucks
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09-23-2016 07:48 PM