4.2 MPFI conversion help

[lafeet]

4.2 MPFI conversion help
hey there

i'm doing a conversion on a 87 yj using 94yj mpfi parts, i
got it all wired up, and i know the mechanical timing is right.

but it will not run , it tries but all it does is pops and sputters, it does not matter how i turn the dist, (i broke the tab thats how i can turn it). i changed the coil, tps, iac, i had extras there not new. it has new rotor, cap, wires, plugs, still the same.

i pulled off the fuel rail to watch the injectors fire, they seem to work fine, BUT shouldnt they shoot just one time per rev.????? there shooting 2 - 3 - 4 times per rev., and i dont thinks thats right.

i'm new to the fuel injection world, and i dont have a way to check for fault codes, i dont know what to do.
can you give me any ideas!!!
thx
jerry

 

[MudderChuck]

Where is your CPS mounted and how are you triggering it?

 

[lafeet]

hey everyone
i'm posting this on a bunch of different boards, hopefully sombody can help

this is a 4.2 mpfi & 4.0 HO head conversion on a rebuilt motor

using 4.0 factory wiring
its in proper time (NOT 180 out)
the firing order is correct
all the valves open and close in relation to the dist.
using factory in tank pump
factory CPS
94 4.0 HO flywheel (so i was told)

everything i have tried to do so far makes no difference in the way it TRIES to run

today i figured i would change the plugs thinking they might be oil fouled. i found out they were not even the right plugs, they gave me the wrong ones to start with, i didnt know i had nothing to compare them to.
put the new ones, thinking this would fix it (NOT) it tries to run exactly the same.

i pulled the codes up
here they are

12 Battery or computer recently disconnected
33 Air conditioning clutch relay circuit open or shorted
(may be in the wide-open-throttle cutoff circuit)
41* Alternator field control circuit open or shorted
54 cam sensor inside the dist.

the only real problem hear is #54
so i got another from a parts store, put it in
TRIES to run exactly the same, no change, and all the codes listed above are still coming up, includind 54

i hav'nt actually check the fuel pressure at the fuel rail (no guage) but i had the fuel rail off and watch the injectors shoot, and the seemed fine, even fired in the proper order 1 5 3 6 2 4, i did notice that they fired more than once per rev.
i dont know if that is right or not.

and its firing on all the cyls i can tell the header gets hot at each exhaust port.

but it will not run, i'm stuck thats why i'm posting this everywhere hoping sombody can help.

thanks much
jerry

 

[MudderChuck]

Where is your CPS mounted? Did you take the transmission with the motor? Reason I´m asking is, I worked some on a 4 liter to YJ conversion a while back, the CPS was a kit mounted on the harmonic balancer. We had to fabricate our own mounting braket to get it to work right. I wasn´t around for the whole operation, but did help some with troubleshooting. He had an automatic computer, on a stick transmission,we had a few extra wires and connectors to deal with.
How did you do initial timing?

 

[lafeet]

the CPS is mounted in the factory spot, on the bell housing

 

[MudderChuck]

Initial timing can cause the symptoms you mentioned. TDC cylinder one, the rotor should be mostly after the number one electrode in the distributor cap. The trailing end of the rotor should be pretty close to equal with the trailing edge of the number one electrode. Most Jeep distributors I´ve had out (never say all with a Jeep) had many more possibilties than correct or 180 out, like you mentioned.
The two push rods to the valves, number one TDC(rockers at equal highth) should be able to spin with your fingers, double check your cam timing.
Garbage in garbage out, the sensors arn´t often good or bad but somewhere in between, if the values don´t jive with exspectations, the computer will sometimes, do strange things. Check the grounds.
Do a compression check on all cylinders just to make sure, the valves are doing the right thing, can also do a cold crank test with a vacume gauge.
I´ve got a tendancy to check the basics before I start changing pieces.
Do a full series of revolutions on the crank, to run the rotor by every cylinder, line up the timing marks and see if number one ends back up where it should be.
Unhook the positive coil wire and crank the motor, if you have an analoge meter, you should be getting one strong pulse per cylinder as the motor cranks. Check the voltage to cam position sensor, should be around five; if I remeber correctly. Clean the die electric grease and/or oil out of the connector, with spray cleaner, brake cleaner whatever.
XJNick knows the electrical side of the motor some better than I do. He probably has some more ideas.
I keep coming back in my mind to the CPS, I don´t think it´s pulsing. If any pin on the CPS has 12 volts, you have trouble.
I spit this out pretty quick, excuse the typos and the disjointed thoughts, gotta go let us know how things turn out.

 

[MudderChuck]

Another thought that popped into my head, the CPS from an automatic won´t work on a stick and vise versa. Been there done that. If the mechanical timing is sound, logic tells me, you could be getting conflicting signals from the cam position sensor and the crank postion sensor.
What did you do for a speed sensor? Is your computer, from a auto or a stick?
Does your fuel rail have a pressure regulator? What did you do for a fuel pump?
Reason I´m asking is that I may be doing a similiar swap soon.

 

[lafeet]

hey everybody
UPDATE

they sent me the wrong fly wheel from the jeep junkyard.
didnt know never seen one before. it was even marked 94 4.0 HO. ive bought parts from them before never had a problem, i guess this makes up for it.

i want to thank everybody for trying to help me. I LEARNED A LOT ABOUT MPFI.

i'll let everyone know what happens after i put the new flywheel in.
thanks again
jerry

 

[lafeet]

Soft top Windows?

hey everybody

just wanted to let you know it started right up with the RIGHT FLYWHEEL, seems to run perfect, still have a lot more to do before its on the road though.

i know now how to wire up a mpfi with a factory harness, its not hard & its a hell of a lot cheaper than buying a aftermarket harness.

thank you again for all your help.

if i can return the favor let me know.
thx again
jerry

 

[XJNick]

Just saw this post, Glad to hear you got it fixed.

Mudderchuck was right in thinking Crankshaft Position Sensor issues, and I was suspecting the exact same thing after reading your first posts. The problem here turned out to be the wrong flywheel, but it was directly effecting the CPS output. This prevented the computer system from working properly due to incorrect voltage pulses being sent to the computer at the wrong times. Basically, the computer was managing the engine blindly. :mrgreen:

-Nick :!: