Ok i bought this truck 1986 ford f150 302 efi a while back and i recently got it to run however i have to plug a obd1 scanner to run/drive it I can get it to run without the scanner but thats by flooring the truck and it only runs at 900 rpm on the floor, it wont rev up without the scanner plug and with a scanner on it acts like a normal truck, i already replaced the tps and fix the wiring up to it, i get a running rich code and ect/act code but those been replaced so im stumped right now
the ecm has been replaced 5x with no luck has any one had this problem i know it gets fuel fine but my only guess is bad wiring or it need air im stumped

 

It sounds like the base timing is off. When you put the truck in test mode with the scanner, the computer sets the timing at 20 BTDC and locks it. I am going by memory on that number, but it's something like base timing +10 maybe 20 degrees. When you unplug the scanner, it's going back to base timing plus whatever it thinks it needs to run, which can vary. If you base timing is too low, it throws the whole thing off.

Go out and loosen the bolt that locks the distributor down just enough so you can barely turn it, but it holds itself. Turn the engine on and do whatever you have to do to make it run by itself. Go out and turn the dist in the direction that makes the engine run faster. Unplug your scanner and see if it stays running. If not, turn it a little more till it will stay running without the scanner.

You then need to set the timing. I would turn the engine off, and clean up the damper marks. Look at them carefully and get some whiteout and paint the 10 BTDC mark, most of the engines are set a 10 BTDC.

Go to the distributor and find all the wires leaving it. Follow the wires from the dist, and somewhere along the way you should find a connector that seems like a jumper. This is your spout connector. You must pull this out to set the timing, it takes control away from the computer. Once you do that, set your timing light up, get the engine running, and set the timing to 10 BTDC. The plug the spout back in and you should be ready to go.

 

Ok im going to try that i been stumped for awhile and i didnt know where else to look at. So before i set the timing do i unplug the spout connector with the engine off or do i need it running 1st then unplug it with the scanner on?

i was also wondering if a faulty reading from ect could cause that because the voltage i get from.it cold is around 2 volts

Also if that doesnt work do you think a faulty reading on the engine coolant sensor might cause that or a bad ground somewhere? It had a wiring issue with the tps before but that the only wiring problem i had so i was just curious

 

so i went out and unplug the spout connector and it fired right off i still had to floor it but i when i let off and it sat and idle but i couldnt rev it so would that mean the timing is off?

 

So i been stumped for awhile on why my truck wouldn't run but thanks to yall i figure it out but i have 1 more problem left my ect has only 2 volts to and i want to know if thats normal? The Ect is new and i tested it and it works fine Im thinking thats why i cant rev my truck without the scanner on would that cause that if it gets a false reading like that? Im really stumped and any advice will be appreciated

 

No. The Engine Coolant Temperature sensor would not cause this at most you would end up with a warm stumble or hard cold starts.

 

do you know what the normal voltage is? I know when its lower the temp its higher the voltage and vise versa so im thinking 2 is not normal

Also on it not revving up like its suppost to do you know what might trigger that i had the tps and tps wiring change/redone and thats all working good and im still stumped

 

What is the V ref you are getting at the ECT ?

 

i get 2 volts cold and hot i would say around 2.03 and it just stay there

 

You should be seeing 5V at the ECT time to trace some wiring and check the V ref at the TPS, ACT, Knock sensor, etc and the self test connector.
You should have 5V for Vref at all.
This may explain why the the truck is only working with the tool plugged in. It may be back feeding and supplying 5V for the V ref.

 

.46 volts = 212F

2.13 volts=104F

3.07 volts = 68F

Here's a link to this circuit on page 61

Electronic Engine Control - ???Gary's Garagemahal

If you look at the diagram, voltage comes from the computer and then you have a common ground on the other side (the black/white). Like Matthew said, unplug the connector, you should get 5 volts between the pins. If you don't put one of your meter leads to the neg battery terminal and then probe both pins and see what you get. If you get 5 volts then , you have a ground problem.

 

I would definitely check the timing. Also check the condition of the harmonic balancer were the timing marks are. If there has been a bad oil leak, look at the rubber insert on the damper, if you see it coming out the damper may have slipped. If it slips, the marks will be off and that can be a problem is someone tried to time it and the balancer has already slipped.

Ist thing to do is put a timing light on it and see where you are at now.

 

One addition here . Check to see you actually have 5V first. Then check the voltage between the pins. If you don't have 5V check for 5V at the ECU if you have it there then time to trace wiring..

 

Im going to pickup a timing gun today but i was curious about it having the running rich code would the timing have something with that as well?

i think i figure it out that since the timing off it isnt getting enough spark to burn the excess fuel meaning when it fire up w/o scanner it can only burn so much due to the motor firing wrong and now that i think about it when i floor it w/o scanner it sounds like its trying to rev up but it maxes out due to the fuel could that just be my problem with the revving thats is off time?

 

What code are you talking about? You pulled the codes? Which codes did you get?