Injectors not injecting
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Freshman User
Joined: Dec 2003
Posts: 33
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From: Maryland/Virginia
Injectors not injecting
I have an 87 F150 5.0L that was rebuilt (not by myself) that I'm trying to get running. I have fuel pressure and ignition, but injectors are not injecting. I checked the voltage at the most easily accessed injector on the drivers side, and it didn't show any juice.<br><br>I was wondering if there's a common mistake that could be made when hooking the wiring harness back up to everything, or if there's a fuse for the injectors I'm not seeing. I replaced the ECU with one I had from a parts truck, with no change in outcome. I've come to accept I may have to pull of the intake manifold, but was wondering if anyone has any suggestions/tips. Also, a source for an injector wiring harness would be good to know too. Thanks a lot.
Posting Guru
Joined: Jan 2002
Posts: 1,346
Likes: 8
From: Baltimore
Here's the schematic for a 88 which may help you.
There are two relays mounted on the driver side wheel well housing. One is the ECC relay and the other one is the Fuel pump relay.
When the ignition switch is in run or start the ECC power relay closes.
This provides 12 volts to the red wire (circuit #361) of each injector. That same 12 volts also powers the EEC (engine computer) and 12 volts for the primary circuit of the fuel pump relay.
As you can see in the schematic, there are two fusible links that protect circuit #361.
Fusibile link N which is hot at all times and fusible link Z which is hot when the ECC Power relay is closed.
There are two relays mounted on the driver side wheel well housing. One is the ECC relay and the other one is the Fuel pump relay.
When the ignition switch is in run or start the ECC power relay closes.
This provides 12 volts to the red wire (circuit #361) of each injector. That same 12 volts also powers the EEC (engine computer) and 12 volts for the primary circuit of the fuel pump relay.
As you can see in the schematic, there are two fusible links that protect circuit #361.
Fusibile link N which is hot at all times and fusible link Z which is hot when the ECC Power relay is closed.
Senior User
Joined: Dec 2007
Posts: 199
Likes: 2
One wire on the injectors should be hot when the ignition is on. Do you have that? If not, trace the wiring back. You might want to look at Autozone.com for the simplified wiring diagram or at alldata for the real one if you can't figure it out from there.
EDIT: F150xlt beat me to it!
EDIT: F150xlt beat me to it!
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
You could verify that the computer is powered up and alive by pulling the codes, there should not be anything stored but if you cannot comminicate with the computer then that norrows your search a little bit to computer power or the box itself. The ignition module(TFI) mounted on the distributor sends timing pulses to the computer to fire the injectors and spark plugs, if it doesn't recieve this signal(PIP) it will not fire the injectors. See www.fordfuelinjection.com for info and diagrams of the ignition system and lots of other good things.
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