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Injector upgrade

X

XJVenom

NAXJA Forum User
Location
SLC, Utah
I've recently installed new 24lb Ford injectors in my rig, but now the engine is running extremely rough. What am I doing wrong?
The engine has been running lean after installing many intake/exhaust upgrades, which is why I was installing these higher flow injectors in the first place.
They are the new, late-model style which are much smaller in design and supposed to provide more efficient automization. I've adapted the injector harnesses to fit to the new style plug. Everything is connected securely. I've considered fitting the new style harness pig tails instead, but I don't want to cut off my old harness if I can't get these working first.
Any suggestions? Should I just get some older style 24lb'ers instead? Perhaps one, or several of the injectors are faulty? (I bought them new on e-bay and they appeared in perfect condition after receiving them.)

Tanks fer da impoot,

Venom
 
What year XJ is it? The HO ones already have injectors about that big IIRC.

How did you connect the new pigtails? If you used solderless connectors, it can cause resistance in the line, and the new injectors may not be getting the right voltage to work properly.

Don't take this as gospel, just some thoughts.

Dan
 
Dan Turner said:
What year XJ is it? The HO ones already have injectors about that big IIRC.

How did you connect the new pigtails? If you used solderless connectors, it can cause resistance in the line, and the new injectors may not be getting the right voltage to work properly.

Don't take this as gospel, just some thoughts.

Dan
Click to expand...

I did not use the new pig tails, as I mentioned in my previous post.
 
I have read elsewhere that the 24lb. injectors should only be used on a stroker motor, because otherwise they would run rich in anything else no matter what bolt-on mods were done. I have the 19lb. ford injectors on mine and they run great, they are a small bump up from the 18.6 IIRC rating on the stock ones, but provide better spray.
 
soulslngr said:
I have read elsewhere that the 24lb. injectors should only be used on a stroker motor, because otherwise they would run rich in anything else no matter what bolt-on mods were done. I have the 19lb. ford injectors on mine and they run great, they are a small bump up from the 18.6 IIRC rating on the stock ones, but provide better spray.
Click to expand...


Besides the bolt-on mods, there has also been internal engine work done.
(Ported/polished head. 5 angle valve job. Increased CR to about 9.1)

The plugs are quite white, indicating it's definitely running lean. Also the engine heats up more and at a quicker rate than prior to the upgrades.

Any other suggestions please?

Thanks,

Venom
 
Measure the resistance across one of the injectors. It should be 16 ohms approximately. Sounds like you may have gotten the low ohm injectors and they aren't being driven correctly. The other thing to do is to measure the fuel pressure at the fuel rail. The flow is a square function of the pressure so if you were to cut the pressure in half, you would only get one fourth the flow. That means a few pounds drop in pressure can radically impact the flow. A quick test is to pull the plug from the MAP. That will cause the computer to go into the preprogrammed mode and dump tons of gas. If it is still too lean, you definately have an injector or pressure problem.
 
soulslngr said:
I have read elsewhere that the 24lb. injectors should only be used on a stroker motor, because otherwise they would run rich in anything else no matter what bolt-on mods were done. I have the 19lb. ford injectors on mine and they run great, they are a small bump up from the 18.6 IIRC rating on the stock ones, but provide better spray.
Click to expand...

You apparently have a non-HO. The early HOs I think used 22 pound injectors, and the later 90s HOs used 24 pound injectors. An HO-based stroker is probably going to need 26 or 28 pounders.
 
Check all your wire plugs to the injectors. I found when I adapted my plugs to fit the late model XJ injectors that it ran a bit rough at first start up. I just played with them one at a time while it was runnig and found one plug was not quite far enough down and suddenly it was smooth as silk. Has been that way ever since.
 
old_man said:
Measure the resistance across one of the injectors. It should be 16 ohms approximately. Sounds like you may have gotten the low ohm injectors and they aren't being driven correctly. The other thing to do is to measure the fuel pressure at the fuel rail. The flow is a square function of the pressure so if you were to cut the pressure in half, you would only get one fourth the flow. That means a few pounds drop in pressure can radically impact the flow. A quick test is to pull the plug from the MAP. That will cause the computer to go into the preprogrammed mode and dump tons of gas. If it is still too lean, you definately have an injector or pressure problem.
Click to expand...

I did measure the resistance on all of the injectors before replacing them. The stock injectors are all about 14.8 Ohms (keep in mind they have over 160k miles on them). The new injectors are all at 15.8 Ohms. If resistance ranges no more than three ohms within spec I should be fine, so the one ohm difference should not affect the perfomance.
 
Gojeep said:
Check all your wire plugs to the injectors. I found when I adapted my plugs to fit the late model XJ injectors that it ran a bit rough at first start up. I just played with them one at a time while it was runnig and found one plug was not quite far enough down and suddenly it was smooth as silk. Has been that way ever since.
Click to expand...

I've checked the connections several times and no matter how I fiddle with them nothing seems to affect it. It's possible I'll have to install the new pig-tail connectors instead. I'm just afraid that I'll have the same problem after doing so, and it will be a PIA to reattach the old connections if it didn't work.
 
I would call benny at hesco performance at talk it over with him I did and if you remember in your last post I stated that I was going to pick up an adj fuel pressure regulator I did swapped it in this morning so far it seems to work well as in I didnt notice a change but when I got on it, it didnt seem to heat up nearly as fast(this is when properly warmed up) as far as power I didnt notice any more but I havent been out on the freeway(more power with WOT)....Ill give you a two day update after more wheel time ;) !!!
good luck
themud
 
themud said:
I would call benny at hesco performance at talk it over with him I did and if you remember in your last post I stated that I was going to pick up an adj fuel pressure regulator I did swapped it in this morning so far it seems to work well as in I didnt notice a change but when I got on it, it didnt seem to heat up nearly as fast(this is when properly warmed up) as far as power I didnt notice any more but I havent been out on the freeway(more power with WOT)....Ill give you a two day update after more wheel time ;) !!!
good luck
themud
Click to expand...


Thanks Mud, lemme know how everything turns out.
 
XJVenom said:
I've recently installed new 24lb Ford injectors in my rig, but now the engine is running extremely rough. What am I doing wrong?
The engine has been running lean after installing many intake/exhaust upgrades, which is why I was installing these higher flow injectors in the first place.
They are the new, late-model style which are much smaller in design and supposed to provide more efficient automization. I've adapted the injector harnesses to fit to the new style plug. Everything is connected securely. I've considered fitting the new style harness pig tails instead, but I don't want to cut off my old harness if I can't get these working first.
Any suggestions? Should I just get some older style 24lb'ers instead? Perhaps one, or several of the injectors are faulty? (I bought them new on e-bay and they appeared in perfect condition after receiving them.)

Tanks fer da impoot,

Venom
Click to expand...

I think the problem is that the injector wiring harness plugs are not making proper contact with the injectors so you're not getting a consistent signal to the injectors for them to fire properly.
You might just have to play around with them for a while like Gojeep did until they fit properly. If you remove and inspect the spark plugs, you might be able to find out which cylinders aren't getting enough fuel and narrow the problem down to one or two injectors.
 
Ok venom get your old ones cleaned and put those suckers back in and get the adj fuel pressure regulator It did worlds of good for me...I no longer have the give it gas and it gets hot real quick problem and it does seem to have more power on the top end(freeway speeds) and especially WOT not a ton but Itll do :clap: ....I know its a lot of cash up front but I would do it again in a sec...also talk to benny yet???
themud
 
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