Ive a 87 4.9 liter straight 6 i have replaced both of the fuel relays , fuel pump and fuel filter . All new oxygen sensors and egr sensors.new coil distributor plugs and wires . But its still cutting off after a minute or 2 of running then it will start right back up again .any body have any idea what is goin on if so please let me no cause ive done everything i could think of

 

pull the codes. it's really quite easy and can save you a lot of money. do a search on it, or, if you are lucky, someone might put up a link here (i would, but don't know how) .
good luck.

 

The truck is an 87 i wish it was that easy lol its like chasing a ghost lol

 

Had the same problem this past fall. Replaced PCV valve, high pressure lines, and done a complete tune up. To find out the all I had to do was increase the octane went from 87 to 92 for a month and everything worked out just fine.

 

unless i am mistaken, a 1987 f series with 4.9 is fuel injected, thus... codes.

 

You could check out oldfuelinjection.com for info on getting the codes -- although I suspect that you won't have any. There's a lot of other info about the older trucks there.

You might try to find out if it's ignition or fuel. Get a timing light and see if the spark drops when it quits.

If it does----

The ignition module (TFI) is known to be unreliable, and is fairly cheap to replace. But, get a good one and make sure that you use the special heat sink grease that comes with it to insure that it doesn't get to hot.

Also, there are a couple of versions -- I THINK that one is gray and the other is black.

Otherwise
The computers are also supposed to have issues. I've read about the electrolytic capacitors more than once. Somewhere -- probably in this section-- there are posts about replacing them.

One other thing -- I'm not sure what you're talking about for fuel pump relays, but there's one relay called EEC power that powers the computer and the injectors. I had an issue on an 89 that turned out to be corroded connections leading to that relay.

Good Luck,

hj

 

I had it running it acts like its running out of gas it has a on the rail fuel pump and a pump in the tank. When it cuts off i go hit the bleeder valve and it has some pressure but its not the pressure i think it should be i dont no ifs the fuel pumps or something electrical to do with them

 

Is the TPS working properly? Possibly something wrong with the fuel injector(s) themselves.