New ecm problems

[Keysd402]

I ordered a new ecm from advanced auto seeing my old one had rust on the circuit board. The rust caused my truck not to have spark, but it still have fuel pressure. after swapping the ecm to the new one I now don't have either fuel pressure or spark. is this an issues with the new ecm or do you have to program these ecms to your vin?

 

[rubydist]

Its also possible you have an issue in the wiring harness that is preventing the fuel pump from running and causing no spark. Are you getting any codes?

 

[Keysd402]

Its also possible you have an issue in the wiring harness that is preventing the fuel pump from running and causing no spark. Are you getting any codes?

For spark it could be wiring, but the fuel system was just working with the last ecm that was in it. I wasn't sure how to get codes off of these older obd1 trucks, any help with that would be appreciated

 

[RonD]

On 1994 and early Rangers spark is done by a separate spark module, computer is only used for fuel injectors

If its a 1986 2.9l then its a TFI module that does the spark, computer does control "vacuum advance" AFTER engine is running, but TFI module does startup spark on its own

So "no spark" was not ECU/ECM related, 1995 and up Rangers used computer for both spark and fuel

Fuel pump should only run for 2 seconds with key on, but it will run for 2 seconds EACH time key is turned from off to on
So repeat key off and on to see if you HEAR the fuel pump running

The best way to test for Spark is to spray fuel into the engine and then try to start, called 50/50 test
If engine starts you have good spark and spark timing, and then dies its a fuel issue
If it it doesn't fire/start then you don't

If it fires or back fires its a spark timing issue

 

[Keysd402]

On 1994 and early Rangers spark is done by a separate spark module, computer is only used for fuel injectors

If its a 1986 2.9l then its a TFI module that does the spark, computer does control "vacuum advance" AFTER engine is running, but TFI module does startup spark on its own

So "no spark" was not ECU/ECM related, 1995 and up Rangers used computer for both spark and fuel

Fuel pump should only run for 2 seconds with key on, but it will run for 2 seconds EACH time key is turned from off to on
So repeat key off and on to see if you HEAR the fuel pump running

The best way to test for Spark is to spray fuel into the engine and then try to start, called 50/50 test
If engine starts you have good spark and spark timing, and then dies its a fuel issue
If it it doesn't fire/start then you don't

If it fires or back fires its a spark timing issue

I checked today, no fuel pressure at the rail, no sound of the pump. all the wiring looks good other then some loose wires with no connectors but ive been told many 80s ford have these do to differences in options.

 

[RonD]

Find the OBD1 connector, it will be between fuse box and firewall on passenger side of engine bay
Looks like this: https://lh3.googleusercontent.com/proxy/NBqTxjxTm9P75dz4c1dp6evolNc8pBYM6WYcivgo0voC0ELk1pCurOGMebbMefRzyQ8JXlwYJtGMATrDrSvK34ooZt3RTGeu4tB1NFAiVJrmE9ySA6DyAlxrB6uqPsNQOPu_f6hirg

Its on the main wiring harness that runs thru firewall to computer in the cab

Fuel pump slot is labelled in picture
Test that slot for 12volts with KEY ON
Should see 12v

If so then use a jumper wire to GROUND that slot, no its not a short
If key is on and that slot is grounded then fuel pump Relay should click closed and fuel pump will start
(if fuel pump starts, then you can try to start engine)

Fuel pump relay is on that side of engine bay, it will have a GREEN base(plug-in), if it doesn't click closed then unplug relay and inspect the base for corrosion

There are 2 main relays
EEC(computer) relay, BROWN Base, it closes when key is ON, it powers the injectors, the computer, and the Fuel pump RELAY(not fuel pump)
When EEC relay closes thats the 12v you see at the OBD1 fuel pump slot
So if there is not 12v at that slot with key on then check/unplug EEC relay and have a look

Fuel pump relay has GREEN Base, the computer controls this relay by grounding it, the OBD1 slot is that ground, computers wire is just looped thru that slot as a TEST port for ground and 12v

There can be a 3rd relay, BLACK base, but only if you have AC(air conditioning), its the WOT relay

 

[Shran]

Common issue that I've run into is the two little wires that are supposed to be attached to the negative battery terminal, in addition to the big negative cable, often are corroded or unplugged and that will cause this exact issue. They are part of the ground for the ECM and fuel system... they should come off the battery, go down about a foot, and into a two wire round plug.

As Ron mentioned, it could also be a relay issue. I've had relays go bad on these trucks quite often.