View Full Version : Starting problem

05-19-2008, 09:07 AM
Ok here goes I have a 87 f250 with an injected six in it, the guy I got the truck off of said that it doesn't start every now and then, it will crank over but won't fire, he said when it won't start it has spark. So he said he wired a light in to the fuel pump wiring so when the light is on the truck starts but if you turn the key it won't (I know it's cheesy but it works for now). So to me it sounds like a sticky relay for the fuel pump, but I'm just not sure if there if one can anybody help me here[cheers]

In The Zone
05-19-2008, 09:51 AM
do you here it prime?
if not check inertia switch they can be defective as well

05-19-2008, 10:04 AM
Where would I find that[cheers]

05-19-2008, 10:06 AM
And the pump doesn't turn on when the light he wired in is off, and from what he said it doesn't get any power to the pump when not starting

In The Zone
05-19-2008, 10:38 AM
typically passenger kick panel area
it will shutoff power to relay effectivley killing the pump 4 wire relay 2 smaller leads are switching from ignition the larger 2 are switched supplying power to pump. use a jumper to pump side to determine path of power is still good..
try running 12v directly to pump from a working relay

had identical issue with the bII
bypassed the inertia switch and threw a new relay in $ 13.00 fix

05-19-2008, 01:03 PM
Cool Thanx Dan I'll give it a shot[cheers]

05-19-2008, 01:40 PM
also fuel pump cut off switch on fire wall behind dash its like a breaker switch

05-19-2008, 02:00 PM
relays Are on the lf inner fender. theres a couple in your other truck at my place

05-21-2008, 07:39 PM
Fuel pressure relay is the green one on either the right or left inner fender... The location changed on the different engines and on different years but it was always the green relay... The brown one is the EEC relay (PCM)... The Inertia switch is a black box with a red tab on the top that is (usually) on the pass side kick pannel... If that was tripped it would not start untill reset (manually) they don't cause much problems as a rule but rules are made to be broken right...lol...
Sounds like a relay problem to me... Good luck...
Cheers Randy...

05-21-2008, 08:06 PM
Thanx [cheers] I'm gonna give it a try this weekend and hope for the best:D

05-23-2008, 09:42 PM
Good luck
Keep us posted...

05-24-2008, 02:50 AM
I have an '87 F-150 with the 4.9 as well .On mine the inertia switch is on the drivers side under the dash.Mine is a small black box with a white tab on the top left side.Its been a few years since I worked on it but I do believe if you can push the tab down that the inertia switch was triggered. You can just push the tab back down and it will reset itself.
After changing countless sensors and wiring it turned out that the low pressure fuel pump ( in the tank) was only working when it felt like it.Once I changed that pump it ran fine.

Good luck on finding the source of the problem. [cheers]