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injector difference?

NorCalChris

NAXJA Forum User
Someone called me today to have me work on their jeep, and they said they swapped their injectors for 91+ injectors. They have a renix XJ. Now I'm pretty sure they are different lb ratings, but are they different style injectors? Do they swap? He said thats all he did and now it wont run. I asked bout his CPS and he said he checked that. Its a crank no start that supposedly ran before he swapped injectors. Anyways thanks for the help in advance.
 
They are plug n pray, except for the 00-01 which have ev6 connectors. Confirm fuel pressure at rail, fuel pump ballast resistor (on driverside inner fender), fuel pump relay, connectors "connected" properly.
 
Where did he get the injectors? verify that they are working? Any cought / stumble sounds or just dead cranking?
 
They are plug n pray, except for the 00-01 which have ev6 connectors. Confirm fuel pressure at rail, fuel pump ballast resistor (on driverside inner fender), fuel pump relay, connectors "connected" properly.

For some reason that just ain't right!
 
I found a little more info from him. Head gasket was replaced, injectors were swapped, and 02. Its here at my place now. I hooked up my remote starter button when you crank it slows wayyy down. Like the valves arn't opening, I pulled the valve cover and manually turned it over and all the valves open. I pulled the plugs and it was the same, real hard to turn over, I loosened the rockers and retorqued to 30lbs, but Im not sure thats the correct torque, I have a manual for my CJ and thats what it said for a 4.2l. Anyone know the torque off the top of their head? Anyways with the rockers retorqued and plugs out it turned over good. Plugs in and it turns over slow again. So I'm not sure whats going on. It seems like its building up too much pressure in the cylinders and its slowing down, but What would cause this? When I turned it over manually all rockers moved down. He said he didn't get any rockers or pushrods mixed up.
 
Bad starter or battery not producing enough cranking amps? The starter is on it's way out on my 88mj and it's acting like a not-enough-juice issue. I don't know if you've ever cranked a working Jeep by hand--it takes some muscle building up compression w/ the injectors in. I threw my 96 gray tops(23.2#@49psi, but 20.7#@39psi) in the 88mj.
 
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Ive turned over working 4.0l quite a few times. The starter looks pretty new, no dirt or anything on it. I charged the battery over night now so the batteries not dead. once he told me the head gasket was replace I figured there might be a problem with the upper end. I have a starter here so I'm gonna swap them out, and if I get a chance take his down to autozone to get it tested. If the starter fix it, then Im going to pull his head and inspect everything. I'd just hate for it to go that way.
 
Are the spark plug wires on the correct cylinders?
 
Model Year, ...Part #, ......Colour, .....Fuel Pressure, ...Static Flow,
'87-'90, ........53003956, ...Black, ........39psi, .................18.6lb/hr
'91-'93, ........33007127, ...Brown, .......39psi, .................21.0lb/hr
'94-'95, ........53030343, ...Tan, ...........39psi, .................21.0lb/hr
'96-'99, ........53030778, ...Grey, .........49psi, .................23.2lb/hr
'00-'01, ........04854181, ...Blue tip, .....49psi, .................22.5lb/hr
 
Are the spark plug wires on the correct cylinders?
yesp, 15-36-24. " too young, too old, just right"
Model Year, ...Part #, ......Colour, .....Fuel Pressure, ...Static Flow,
'87-'90, ........53003956, ...Black, ........39psi, .................18.6lb/hr
'91-'93, ........33007127, ...Brown, .......39psi, .................21.0lb/hr
'94-'95, ........53030343, ...Tan, ...........39psi, .................21.0lb/hr
'96-'99, ........53030778, ...Grey, .........49psi, .................23.2lb/hr
'00-'01, ........04854181, ...Blue tip, .....49psi, .................22.5lb/hr
Thanks Tayln.

I just eliminated the starter, I swapped in a known good one and Its doing the same thing. I pull one spark plug and it turns over good.I tried that on a few different spark plugs and it seems that no matter which one I pull its fine. Im going to pull the intake/exhaust off to see more, I was hoping it would come to this, but I dont see any other option. The only thing I can think of is a rag or something might be in his exhaust? The manifold isn't hooked up so I know its not a plugged cat.
as always any ideas are welcome.
 
so I just pulled the Intake manifold and exhaust manifold and about 2 cups of fuel poured out of it.??? Possible stuck open injectors? I was surprised at how much fuel was in there. I did notice earlier that once I put all the plugs in, it turned over normal, but as soon as I turned the key to try and start it at would turn over slow and try to kick back. Maybe it's flooding the cylinders full of fuel?

**edit** I forgot to mention he said these injectors are used off a 91.
 
The injectors are stuck open. THere should be approximately ZERO gas in the intake manifold.
Injectors don't have much of a shelf life. Once the gasoline evaporates out of them, the sealing surface inside the darn thing can develop miniscule amounts of rust & the open-close mechanism inside can do the same. They gut gummy, or even a tiny amount rusty, and they stop opening closing and sealing when closed properly. Game over.
You will probably want to replace the plugs due to fuel fouling (or at least shoot them with carb cleaner and a toothbrush) and change the oil, too. Once gasoline leaks down past the piston rings and hits the oil, the lubrication value goes to crap.
 
SO I hooked the fuel rail up, turned the key on and watched the #6 injector drip every two seconds. Thats the only thing I found wrong. I guess that cylinder was Filled to the brim with fuel and slowing down the whole rotating assembly. I have his old renix set, Im gonna swap them on the rail and see if they leak at all, then see how well they fire. Hopefully better then these ones.
 
x2. The injectors are stuck open. That the problem of using old injectors. Especially if they sat a while. The walls of the intake may have a light coating of fuel, but not puddling.

Also, if the cylinder was had a lot of fuel in it you could have possibly bent a rod. But usually with just cranking you get away ok.
 
Welllll......I just swapped injectors, put the manifold back on, hooked all the sensors back up, tried to start it and it kicked back again? If a rods bent, timings off and that could be the issue correct? By the time the pistons coming up the valves could already be closing. I'm thinking I need to pull the head and measure how far up the piston comes up compared to the rest. Other then that, I'm all out of ideas.


Head gasket was replaced, rockers were a little over torqued, re torqued the rockers, installed everything, #6 injector was leaking, pulled the manifolds and a bunch of fuel poured out of #5&6 runners. let the fuel dry up, swapped out 91+ injectors for the renix injectors, installed everything back on, tried to fire up and it still kicked back. When the plugs are out it turns over normal.
 
nvr mind. You've indexed the dizzy correctly?
I thought about this before, but forgot to mention.. can't hurt to try, if not done already.
 
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