Tbone289

A couple of weeks ago I did a thorough cleaning of the throttle body, IAC and all grounds on the XJ, reset the PCM and afterwards it was running smoothly and starting nearly instantly.

This morning I R&R'd the injectors (upgrade to 784s), reset the PCM again, and now cold starts are are sluggish, taking 3-4 seconds of cranking. If I shut it off and restart it soon after (within a minute), it starts as it was before. It runs really smooth with the new injectors, but cold starting has definitely been negatively affected.

Should I wait for the PCM to learn for a while, or is there something I should start looking into? I'm guessing that it might be draining back fuel as it sits, but I haven't rented a fuel pressure gauge to see how quickly it bleeds off. I've owned this XJ for ten years, and it's always cranked over really quickly, even after sitting for a long while (weeks or even months at a time).

The only thing besides the injectors that was disconnected and reconnected during the procedure was the battery and the IAC. The battery, which is only a couple of months old, has a full charge.

Any help would be greatly appreciated. TIA

CurrySoSpicy

When I did my 01' I had a few rough starts but not what your experiencing. I would definitely confirm what happening with a fuel pressure gauge. That would tell us a lot.

THX-1138

Yea, I had a single rough start with a brief choppy idle. I think you have something else going on beyond your PCM re-learning.

Tbone289

Well, I think you're both right that it's an odd problem, and I think I found it.

I started re-tracing my steps since yesterday, basically since I shut it off last night until I did the injectors this morning. I was bored in the shop late last night and decided to clean and grease some connectors and re-route, tape and zip-tie some of the associated wiring around the dipstick area C107, TCA, TRS/NSS, etc.) because the wires have been bound-up there and rubbing since I've owned the XJ. I've double-checked and triple-checked those connectors several times today and knew they were good, then it struck me that I also disconnected the coil capacitor while I was doing that.

I just went out to the shop 5 minutes ago, looked at the capacitor and could tell the connector was just barely hanging on. I reached down there and the damn thing nearly fell off the capacitor before I clicked it into place.

I think that will prove out to be the issue. I'll report back on how it starts in the morning. If it's good I'll go ahead and reset the PCM again for good measure.

Thanks for the replies fellas!!

Love the user name THX!

Tbone289

Wait.

Isn't the capacitor just for filtering noise? Maybe this isn't it... We'll see.

EDIT: That wasn't the problem. I'll rent a fuel pressure gauge tomorrow.

moparado

If you're talking about your 2k, it has a coil pack thus no coil capacitor.
The capacitor you're probably referring to is for ignition EMI noise suppression.

My 4 hole story.
When i swapped over to the 4-holers, it initially started a little rough but the 2nd and later cold starts were just ok taking a second or two of cranking.
However, with hot starts it would take 4 to 6 seconds of cranking. No PCM reset.

Sent those injectors back and re-installed the replacements.
Again no PCM reset.
Cold starts now, instant, just by touching the key.
Engine starts so fast can't ever hear the starter crank.
Hot starts now, a second or two of cranking (with my efan delay).
A little longer crank if i forget to turn on the efan delay in hot weather.

Other than a fuel psi issue, maybe one of the injectors is leaking, O ring damaged or just a defective injector in the bunch?

Tbone289

Yes, I was referring to the ignition capacitor that filters noise.

I rented a fuel pressure test kit this morning. Here are the results:

Pressure after priming 8-10 times: 48 PSI
Pressure at idle: 46.2 PSI
Pressure leakdown: 30PSI after 28 minutes

Obviously I have pressure bleeding off fairly quickly and my idle pressure is within spec (49.2 PSI +/- 5 PSI), so at this point I needed to determine if the injectors were leaking or the check valve in the pump was the culprit. I took off the throttle body elbow and could smell a faint whiff of fuel, but probably not enough to indicate the injectors were leaking. For good measure, I disconnected the injectors and pulled the rail, flipped it over 180 degrees and primed the rail back up to full pressure again. There wasn't a single drop of fuel from any of the injectors.

I would like to be able to clamp off the fuel line to further test leakdown through the pump check valve, but I don't have a proper adapter for that. The FSM indicates that leakdown to 0 PSI after cooldown is normal, and that the pump should prime the fuel back to normal pressures in 1-2 seconds before starting. I have to prime mine at least 4-5 times to get it back to normal pressure.

I would like to conclude at this point that I need a fuel pump module. Is there anything else I should test?

freegdr

If it did not have this issue b4 injector upgrade I would just reinstall old one see if issue goes away. JM2CW

Tbone289

Great suggestion freegdr.

Already did, with new orings. Problem gone. I guess I got a set of leaky injectors. Odd thing is that they never really drained fuel. I guess they just let air into the system, allowing the fuel to drain back to the tank.

CurrySoSpicy

where did you get your 4-holes from? We have a gent here on the forums who sells injectors. He does a fabulous job.

freegdr

Could of been just sticking and when warm they frred up.

Tbone289

Yeah, I know... I contacted him and was impatient awaiting his reply and went with an eBay source with good feedback. Lesson learned. If I decide to do the mod again, I will keep it "closer to home".

Tbone289

That's a possibility as well. Hard to tell.

freegdr

I got mine from local you pull those have been in use recently and there were no issues. Just a thought.

Tbone289