I just installed my MAF conversion kit. In the process it converts the firing order from the normal 5.0 to the 5.0HO/5.8 order. I have everything back together and I went to start it and it started up, but its skipping and not running correctly. I believe it has something to do with the wiring and not fuel. To change the firing order, I moved the 3 and 5...4 and 7 wires (i think those are the right ones if my memory is correct) around on the distributor. Is that the correct way to do it (or is there more to it then just swapping the wires on the distributor)? I had to re-route the wires and it makes it a pain in the butt because they cross easily and don't wire nicely. Did I incorrectly change the firing order? Also, when it starts, it turns over for maybe 1-2 seconds longer than normal before it fires. Any insite into the problem? thanks.

 

Bump

 

The physical firing order of the engine is still the same - 1-5-4-2-6-3-7-8. The injector wiring harness is wired for the other firing order, so you will need to switch 3,5 and 4,7 injector wires, either at the computer or somewhere in the harness. I think the pin numbers in this diagram are the same, but double check with a multimeter first, so you don't accidentally move the wrong wires.

 

might be a lil out of time?

 

Not out of time, unless he moved the distributor, which I don't think he did. It's all in the firing order.

 

if the distributor wasn't touched, then why would the fireing order change?

 

That's the point. He swapped plug wires instead of swapping injector wires, and that resulted in the engine running bad. Took care of that in my first post. Sorry if I sound like a smart a$$, I'm not trying to be.

 

The conv. kit I purchased came with the 1-3-7-2-6-5-4-8 firing order. My stock order is 1-5-4-2-6-3-7-8. I thought all I had to do was swap the 5-3 and 4-7 wires on the distributor and it would make the spark plugs fire in the 1-3-7-2-6-5-4-8 order. I can't easily swap the injector wiring, I'd have to take the whole manifold off again. I'm going away tomorrow and I'll be back tomorrow night to work on it. I edited my "bump" above to say something else but it didn't come through (Ken must have been changing over the software at that time). Basically I said I can't change the firing order of my motor to the HO order w/o changing the camshaft right? I'll try to swap the wires back and see what happens.

 

You can't physically change the fireing order of any engine without changeing the crankshaft.

so, if his new kit makes it fire 13726548 then switching the wires on the distributor shoudln't be a problem, if its not an electronic distributor.
cause the spark is going to the right cylinder at the right time.
just as long as it fires 1, and it goes to 1, its fine.
2 to 2, and so on.

what i dont understand is what he converted i guess.
cause, if the distributor wasn't touched, the wires from the distributor should stay the same, and like i said, unless the crank is changed, the pistons still move in the same order.

So, looks like hes haveing fuel issues then. The fuel isn't being injected at the right time. and its burning leftover fuel that wasn't expunged through the exhaust.

 

Unless I am mistaken, I'm pretty sure that isn't true...


I swapped the plug wires back to where they were before and it now seems to be running fine, something still seems incorrect I'm not sure why that would work, but atleast it's running. I just put new plugs in it so I think I should check the plugs to make sure its not running rich after a few miles.

 

Mustang, you're on the right track. What EPNCSU is saying, is that you didn't physically change the "spark plug firing order", but you did indeed change the fuel injector firing order with the install of the MAF swap. You distributor gets its position from the camshaft which either has a 15426378 (your camshaft) or 13726548 (the HO firing order). Unless you DID change the cam, and didn't tell us, you need to either do that (change the cam) or reset your spark plugs firing order to the original and THEN pull the fuel injector wiring harness and rewire that to the 15426378 order.
I did the opposite when I converted to MAF. I had already installed a HO cam out of a 91' HO motor, as well as the new HO spark plug firing order 13726548, so when I installed my FMS MAF kit, I had to rewire the fuel injector harness to the new HO firing order.
Do this first. Before you even start cutting wires. Just put your plug wires back to the non-HO firing order and fire it up. You should immediately notice correct firing, but MABYE with a slightly rough idle. You are still injecting fuel into the correct chambers, BUT instead of running in SEFI like you hoped for with the swap, you're now back close to running Bank-to-bank again. (same concept) Swapping the injector wiring around will give you true Sequential EFI.

Good luck.

Luke

Talyn, I believe you mean CAMshaft, not crankshaft??

 

Well it idles smooth, but the computer is an A3m-1 (Eric you asked...). I would rather try to change the pins on the connector if it's easy. If i have to re-wire the harness i'd have to take the upper manifold off and that was a pain, basically do this job all over again. The kit originally came with the non-HO order, but the guy I bought this from changed the pins to the HO firing order. He offered to swap it back but I declined thinking I wasn't going to install this kit until I got my new motor (which used the HO). I decided to throw the kit on my currect motor to see what kind of a difference it would make (its the FMS kit). I have not changed the camshaft, or anything on the motor.

 

Check out this diagram:

These are the pin numbers at the computer plug. You won't have to do anything with the actual injector plugs themselves. Swap 3 & 5 (pins 12 and 14), and 4 & 7 (pins 13 and 42). You have to pull the red plastic retainer out of the computer side of the plug. Then get a small screwdriver (glasses flat head works nicely) and pull back on the clip enough to get the pin to release. It will pull out the back of the plug. Just swap those 4 wires and you are good to go.

 

The pistons are physically connected to the crank. SO unless you pull apart the engine, swap the crank and put it back together, the pistons will always go in the same order.

The camshaft does the valves, and spins the distributor, which creates the spark.

I'd say its all with your Fuel injection timeing, or distibution. =)

I guess working on a motorcycle has helped me out a lot with engines.

 

How can you change firing order with out changing the camshaft??? Am I missing something here????

Al