VetteNoob

Installed some 24lb injectors this weekend. The reason the injectors were replaced is because I suspected leaky injectors. Since, my coolant temp has been climbing faster and remains higher than normal (still within safe range tho). I also replaced the cap and rotor while I had the extra room to work.

The oil temp is roughly the same as before.

Could the new injectors and cap/rotor be causing the engine to run leaner and thus the higher temps since I no longer have a leaky injector adding extra fuel to the system?

Im planning on checking the timing again to make sure it didnt change for some bizarro reason when I replaced the cap. It was set at 6* previously.

Any other thoughts? Thanks!

65Z01

You realy should have installed an AFPR before upgrading injectors, but now it would be a good idea to check fuel pressure.

With 25lb/hr injectors you are likely running rich with the same fuel pressure as before.

bogus

I would be concerned, that after time, the rich condition could hurt the cats.

bad cats would also cause the engine to run warmer!

how old is your coolent? have you cleaned out the inlet?

vinnies87

What is an AFPR? Education time?

subman

Adjustable Fuel Pressure Regulator. Runs about $75.00. Easy to install. Remove plenium (again) and follow instructions that comes with the AFPR. Set pressures (someone else with more experience jump in here!) I have 21# Ford's on my 91 L98 and ended up running 42#'s.

VetteNoob

Thanks for the comments guys.

The FP gauge shows good FP. 38psi with vaccum connected at idle and 42psi when it is disconnected.

I dont think Im running rich, but that's just guessing. Im actually getting better fuel mileage now with the new injectors. Also, You'd think if I was running a "little" rich, the temps would be cooler, right?

I dont have a functional cat anymore so I know it isnt clogged :D

But to rule it all out, how would I go about checking if I am running rich?

0ski_dwn_it

vettenoob,

The AFR at cruise, should still be around 14.7 with the car in closed loop, and the ECM adjusting the pulsewidth. If your injectors were leaky before, most likely it was only leaky at shutdowns or when the car wasn't running. So I doubt you are running much different AFRs than before. There is always the possiblility it was dumping tons of fuel in to the car, but driveability would have been VERY poor if that was the case.

I would lean towards your radiator getting clogged. Pull it lately to see what goodies you have between the rad, and the condensor lately? All it takes a plastic bag or something to get sucked in there. Or over time leaves etc.

Beyond that I am a bit concerned at what you said your FP was when the car was idling with the vac line on and off. 4psi differential is very little to have.

You should see 5psi drop for every 10"vac your engine pulls. Get a vac guage and let me know what your car if pulling for vacuum. If its pulling around 15" or more, then you should be seeing a min of 7.5psi drop between vac line on and off.

If you don't see enough drop then your going to have problems with the injectors. Its VERY VERY important to have a constant pressure on the injectors. This is what the regulators purpose is for.

Be sure to check both of those out. :cheers: :cheers: :thumbs:

Nathan Plemons

:iagree:

Something doesn't sound quite right with the fuel pressure. My car with the Hot Cam doesn't pull as much vacuum as a stocker would and I still get a pretty good fuel pressure range. At idle it's around 38, WOT it will go upwards of 46

VetteNoob

Cool.

Driveability hasnt changed all that much. I dont think I was dumping fuel. I think it may have been a small leak. I do suspect my FPR to be defective since it is still dropping FP when the engine is not running and both the injectors and fuel pump are relatively new.

Looks like Im buying a vaccum gauge on my way home today. Where do you recommend I connect the vaccum gauge to get a good reading?

I'll also double check the FP with and without vaccum and post those.

I checked the gap between the radiator and condensor not more than a month ago so I hope it is still clean, but I havent looked infront of the car since I've noticed this.

Also the coolant was replaced last year when I replaced the radiator so it "should" still be good.

Thanks!

65Z01

I was thinking that if your O2 sensor were bad heaftier injectors might lead to the clogged cat, if it were nearly expired. To check for a bad O2 sensor use the method on my site (link in my sig. below) to see if the ECM is going into and staying in closed loop mode. To check for a clogged cat, connect a pressure gauge into the O2 sensor location and see if there is more than 2-3 psi of back pressure.

If fuel pressure is leaking down too fast:
-clamp the return line, if it drops it's not the AFPR
-clamp the pressure line, if it drops it's not the FP check valve
-if it still drop after the above checks, send your 9th injector to Rich at Cruzin Performance for a rebuild/replacement. Of course you could pull the fuel line from the rear of the fuel rail, plug the fuel rail fitting and repeat the above leakdown tests to verify it was leaking.


[Modified by 65Z01, 1:39 PM 9/10/2003]

VetteNoob

Double checked the FP.

Vaccum connected reads 34.5
Vaccum disconnected reads 44.5

Dont think there is a vaccum problem. The pressure with vaccum connected seems a tad low, but not horribly bad, right? Isnt 37-38 normal?

Should I still check vaccum?


[Modified by VetteNoob, 6:53 PM 9/10/2003]

0ski_dwn_it

VetteNoob,

That sounds about right now. A few thing. You installed 24# injectors. When you did this, did you disconnect the rad hose? If so the system might have air trapped, or might not be 100% full. Pull the rad cap off, rev it to about 2000 RPM , fill the rad, replace the cap, then let the RPMs come down. This will "pack" the system. Make sure you see water flowing in though the radiator, that makes sure the Tstat is open. Then do as I described.

Second. The fact that you now have 24# injectors is going to mess up your tune quite a bit, if its set up for the stock size injectors. Throttle response etc is all going to suffer. Everything needs to be recalibrated with a custom chip. That will not solve your temp problems, well it could with some fan temp changes, but that is not the reason most likely you are seeing hotter temps. By the way, what temp increase did you see?

:cheers:

VetteNoob

ski_dwn_it,

I didnt have to disconnect the cooling system when I swapped out the injectors. I agree that I will probably need the car tuned to work better with the injectors.

The major in temp is that it rises quicker than before with about a 5-10* increase in operating temps. Now instead of being around 190s* in slower moving traffic, I will see low 200*s. Not critical by any means, Im just trying to understand/account for the temp change is all.

vetracer

Just curious, when I went to 24# injectors, my car had a hesitation problem when accelerating from low RPM. I've seen others on the forum with the same problem. I couldn't get it to go away until I put the stock injectors back in. Did you notice this problem, or is the throttle response the same? :lurk:


[Modified by vetracer, 1:55 PM 9/11/2003]