Skip to main content ↑ ↓
Topic: HO Swap Fuel Problem (Read 8534 times) previous topic - next topic

HO Swap Fuel Problem

Hello everyone.  My '87 Cougar has been at the mechanic for a while now because he was supposed to swap an HO into it for me.  He got it installed and hooked up, changed the ECM, and it won't start.  I just got off the phone with him a few minutes ago and here is what he says;

The motor has good spark and good fuel pressure.  Everything looks fine except the fuel injector pulse width.  He does not see the ECM sending the grounding signal to the injectors to cause them to open and spray the fuel.  He says that power is good to both sides of injectors.  He has changed out the ignition module at the bottom of the distributor and that did not fix the problem.  He has also tested the harness for any shorts or other abnormalities but everything looks good.  It is worth mentioning that the original 5.0 that was in the car ran fine.

The computer I got with the HO motor is an E7SF-12A650-E1A.  It was marked as being from an '88 Mustang.

Is there anyone who can suggest any tests that he can perform that will help track down the source of this issue?  Any information anyone can provide would be helpful.

Thanks.
-Jim
1987 Cougar LS 5.0

HO Swap Fuel Problem

Reply #1 –
This may be a stupid question, but are you using the same firing order as you used before the swap?
FOXLESS!!

1994 Lincoln Mark VIII

HO Swap Fuel Problem

Reply #2 –
That is a good question and I'm sorry I forgot to include that information in my original post. 

The answer is no. The mechanic knows that the HO firing order is different.
-Jim
1987 Cougar LS 5.0

HO Swap Fuel Problem

Reply #3 –
Did he remember to route the wires counterclockwise  on the cap ?




 ask me why I asked that :mullet:
Fox-less at the moment

HO Swap Fuel Problem

Reply #4 –
If he stuck a noid light on it and didn't see the injector fire, I would check the wiring between the ECM and the Ignition module. 

Put the old ECM back in and see if the injectors fire.  If they do, start checking ECM grounds and try to bum an ECM from someone.
My car is a gravity hybrid.  The gasoline engine gets me up the hills, and gravity gets me down.

HO Swap Fuel Problem

Reply #5 –
Quote from: 88CougarGT;339151
I
Put the old ECM back in and see if the injectors fire.  If they do, start checking ECM grounds and try to bum an ECM from someone.


X2, it should even run on the orig ECM, though not very well...

HO Swap Fuel Problem

Reply #6 –
Thanks for the information.  I talked to him again today.  He already checked the grounds on the ECM and they are good.  He's going to try to start it using the original ECM with plug wires rearranged to coincide with the different firing order to see if that causes the injectors to work properly.  I hope it does, because that would point to the ECM as the source of the problem and that is a fairly easy fix.
-Jim
1987 Cougar LS 5.0

HO Swap Fuel Problem

Reply #7 –
If I am reading this correctly,
The cam determines firing order not the ECM , rerouting the firing order will make it run py if it runs at all
Fox-less at the moment

HO Swap Fuel Problem

Reply #8 –
Quote from: hypostang;339299
The cam determines firing order not the ECM , rerouting the firing order will make it run py if it runs at all


Agreed.  Just stuff the old ecm in and see if it runs/tries to fire with the HO plug routing.  Beware, it may try to walk its way out of the engine bay.
My car is a gravity hybrid.  The gasoline engine gets me up the hills, and gravity gets me down.

HO Swap Fuel Problem

Reply #9 –
the car will run with the ho firing order and a non ho computer . i drove mine for a few days like that actually ran decent .sounde3d like it had a huge ass cam at idle tho.gotta be pinched wire/ bad ground or computer problem. is he a reputable mechanic or a backyard mechanic?

HO Swap Fuel Problem

Reply #10 –
yes the cam determins the firing order how ever the computer programmed to open the injectors at a different firing order

HO Swap Fuel Problem

Reply #11 –
He is a reputable mechanic that has had his own shop for quite a while, but he is more of a Chevy guy. Unless the harness was somehow damaged during the engine swap, I don't see how it could be the source of the problem seeing as how the car ran fine with the original 5.0 and ECM.
-Jim
1987 Cougar LS 5.0

HO Swap Fuel Problem

Reply #12 –
so you used the non ho harness? i did on my swap and had no problems. the only difference i could find was different temp sensors etc...

HO Swap Fuel Problem

Reply #13 –
As others stated when using SO ECU, leave the plug wires in the HO pattern, the plugs MUST fire when piston is at near TDC on the compression stroke... If you change the wires to the SO pattern, those cylinders will be firing on the end of exhaust stroke...

HO Swap Fuel Problem

Reply #14 –
I got it.  Plug wires stay the same.  He thinks he can source a good speed density HO ECM so we'll see if that one works.  I haven't heard back from him on whether the original ECM worked.  I'll call him later today.
-Jim
1987 Cougar LS 5.0