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Need help please, new motor, now pings bad

Posted: August 1st, 2012, 8:20 am
by Tuffy
Hello all,

This is my first post, been surfing the site for a while now, great info. Sorry for such a long first post, but I need some help getting a freshly rebuilt 258 to run correctly.

I had my 1987 258 4.2 with junk yard MPFI blow up last fall, #2 piston broke apart. The motor had over 100,000 miles on it. I found a different 87 block and had it professionally rebuilt. The motor was bored .030 over, with stock pistons, a comp cam Xtreme 4x4 X4250H-13. I am running a 4.0 head, the head was milled flat, nothing more, as was the top of the block, not sure how much the block was taken down. I run a stock 4.0 MPFI junk yard obtained fuel injection. The compression ratio was raised to around 9.7-9.8 per the engine builder. The motor was broke in correctly to break in the cam and such. While breaking in the cam, the exhaust system got red hot all the way to the muffler, not sure why as it has not done this since. The motor however never runs over the normal temp, no overheat condition. When driving the motor pings at mid throttle. If I keep the jeep in neutral and rev up the motor it makes a strange noise at around 2000 rpms. The engine builder seems to think it is the ping as it sounds like it is in the exhaust manifold. The engine builder checked the compression of each cylinder, this is what they are:
1-181
2-183
3-180
4-181
5-179
6-183

I am stumped, as I do not know where to go from here. The engine builder is a reputable local builder, he knows how to build a good motor, but he knows nothing about the MPFI. I am running stock MPFI components from the junk yard. I had these components on the stock motor for 3 years with no problems before the motor let go last fall. The motor was tired, I knew that.

The motor builder spoke with Comp when choosing the cam and it was recommended by Comp. We checked the plugs, they are very clean and look new, it is clearly running lean. The plugs are almost white. I am running fresh 91 octane gas. The motor pings quite badly. I am afraid to drive it and have not done so. The motor runs very smooth, just has major pinging at moderate throttle. I am running a cold air intake with an open element air filter. I am running the spark plugs recommended by Hesco with their MPFI kit, they are champion RC9YC I believe. I am using the single line fuel injection from a 95 4.0. The fuel pressure while at idle is about 50 psi, and is about 46-47 psi while at hard throttle application while driving. The injectors are stock and are probably the original stock injectors from 1995. The timing was checked and found to be about 12 degrees at idle if I remember correctly, per hesco this is correct?

Is there a way to see the timing and what it is doing using a mopar scan tool? Can the timing be adjusted using the scan tool? It would be interesting to see what timing is doing while driving. I was unable to figure out why my last motor blew up, wondering if it was running lean as well the whole time and finally let go after 3 years. I do not however put many miles on per year, about 3-4,000.

I am stumped, the wife is pissed as I spent a fair amount of money on the motor, and we cannot drive the Jeep and it sits in the garage. Please help me get this thing running correctly and strong. I feel the motor was built well and should have great power, it just needs to be tuned correctly, but I am not quite sure how to do that.

I was told to obtain a wide band 02 sensor and check the air/fuel mix, I am working on finding one at the moment. Where do I go from here?

Re: Need help please, new motor, now pings bad

Posted: August 1st, 2012, 9:14 am
by CobraMarty
Tuffy wrote: I was unable to figure out why my last motor blew up, wondering if it was running lean as well the whole time and finally let go after 3 years. I was told to obtain a wide band 02 sensor and check the air/fuel mix, I am working on finding one at the moment. Where do I go from here?
Wonder why #2 cylinder blew? Bad #2 injector? Too high compression and it is pinging? Maybe a MAP adjuster to richen it a little. Wideband o2 sensor is a smart ides.

Re: Need help please, new motor, now pings bad

Posted: August 1st, 2012, 4:43 pm
by SilverXJ
Tuffy wrote:The motor was broke in correctly to break in the cam and such. While breaking in the cam, the exhaust system got red hot all the way to the muffler, not sure why as it has not done this since.
Not uncommon for a cam break in.
We checked the plugs, they are very clean and look new, it is clearly running lean. The plugs are almost white.
Looking at the plugs is a poor way to determine correct AFR on a fuel injected engine. A wide band O2 sensor and gauge is the best way.

First I would get the wideband. Then get some 24 lb injectors. That could fix your problem. If it still doesn't a MAP adjuster may. Quite cheap from strokedjeep.com

Re: Need help please, new motor, now pings bad

Posted: August 1st, 2012, 7:24 pm
by Tuffy
What should I be looking for when using the wide-band 02 sensor? Is this a one time check? What value or numbers should I see and what is considered normal? What 24 lb. injectors do you recommend? Where do I get the injectors from?

Thanks in advance.

Re: Need help please, new motor, now pings bad

Posted: August 2nd, 2012, 6:35 am
by gradon
Have you tried 93 octane yet?

Re: Need help please, new motor, now pings bad

Posted: August 3rd, 2012, 5:48 am
by Tuffy
The jeep is filled with fresh super unleaded (91) octane. This is the highest octane in our region. We do not have 93. Anyone else have this problem? I am very frustrated with this, it never pinged before rebuilding the motor. We didn't feel raising the compression ratio this small amount was going to make such a huge pinging problem.

Thanks

Re: Need help please, new motor, now pings bad

Posted: August 3rd, 2012, 6:15 am
by SilverXJ
What did the fuel injection system come off of?

Re: Need help please, new motor, now pings bad

Posted: August 3rd, 2012, 7:29 am
by gradon
The fuel rail must be from a 96+XJ or 97+TJ if it doesn't have a return and is ~49psi. Maybe the cam sensor in the dizzy is a bit off. I ran the RC9YCs for the first 4 years and don't think those are the problem. You very well might need larger injectors as said earlier.

Re: Need help please, new motor, now pings bad

Posted: August 3rd, 2012, 11:41 am
by Tuffy
The timing chain and gears were set correctly, at least that is what engine builder says, plus it matches up with TDC when checked, so I don't think that is the problem, plus when the timing is checked at idle it seems to be ok. The MPFI is from a 1994 Grand Cherokee, the head, MPFI, and exhaust manifold all came from this vehicle. The ECM came from a 1992 or 93 Cherokee XJ, would that matter?

How do I know if I need injectors, and what size injectors do I go with?

Re: Need help please, new motor, now pings bad

Posted: August 3rd, 2012, 12:07 pm
by gradon
Take a pic of the fuel rail, cause "single line" and "50psi" all point to obd2/96+ setups, but you say you have a 94 ZJ 4.0 setup, which should be [email protected] and [email protected](test w/ the return line vacuum disco'd) and have a return line. Granted, I haven't played with the carbed 87-90YJs, so maybe they had a single line to begin with and you upped the fuel psi with a newer pump, but then you chose to run a pcm that was tuned and made for the return setup and lower psi. You can have the timing chain set up correctly(cam to crank correct), but the cam sensor in the dizzy can still be off, thus the fuel sync off. If you mark the base of the dizzy where #1 post is with the cap on, then remove the cap, and rotate the engine by hand to 0* at the end of the compression cycle(might have to spin almost 2X), the rotor should be just past(CW) the #1 spot.

Re: Need help please, new motor, now pings bad

Posted: August 4th, 2012, 3:54 pm
by Tuffy
Gradon,

Yup, the dizzy points as you state, checked that. The fuel system is correct, it how the ZJ's came in 94,95 prior to OBD 2. I checked with Hesco, they state the fuel pressure is right on. This setup ran great before the motor blew last fall, I drove this setup 3 years with not a problem. You do however bring up the point about the ECM being from a system with a return fuel system, not sure if that would really matter though, as Hesco sells an upgrade kit for their older return fuel system to upgrade it to the single fuel line to prevent issues with heated fuel being returned to the tank.

I really feel this has something to do with the compression ratio and the amount of fuel, as the plugs are white which indicates a lean condition. The fuel injectors are old original oem injectors. If I tried new injectors, what should I go with, many have stated 24 lb, but what injectors are 24 lb? I have no problem purchasing new injectors, just need to know what size and type. Keep the help and ideas coming. Later this week I will be putting the jeep on a wide band 02 sensor to see what the air/fuel ratio is, as well as whistling the motor to get the exact compression ratio. The head gasket that was used was a stock Felpro brand, not sure what the thickness is.

Thanks

Re: Need help please, new motor, now pings bad

Posted: August 4th, 2012, 5:36 pm
by SilverXJ
In all the years of driving my 95 ZJ I never noticed if the fuel rail has one or two lines going to it. I checked the FSM and it hints towards a single line, saying the FPR is on the fuel pump. However, the FSM also states that the fuel pressure should be 39 PSI, not 50 PSI. How are you dealing with a lack of auto transmission attached to the PCM? What fuel pump are you using?

Re: Need help please, new motor, now pings bad

Posted: August 6th, 2012, 7:12 am
by Tuffy
According to info I received when I first injected the old motor, as well as from Hesco, the 49 PSI is correct for fuel pressure on the single line system. I am using a E2000 in-line fuel pump (for a ford) and then use a WJ (Grand Cherokee) fuel filter/regulator to regulate the pressure to 50 PSI. This has worked for the past 3-4 years great, I had no pinging on the old engine. This way is a very common per the internet way of piecing together the MPFI system for a 258.

Re: Need help please, new motor, now pings bad

Posted: August 6th, 2012, 5:39 pm
by gradon
Most injectors are rated @43.5psi, so you'd want injectors that'd be rated 22.6#@43.5psi in order to be 24#@49psi. You'd want ones with ev1 connectors. I'm sure you can find a thread around here that Silver has given p/ns for.

Re: Need help please, new motor, now pings bad

Posted: August 6th, 2012, 6:05 pm
by SilverXJ
The two I recommend are the Bosch 0-280-155-784 (Neon) and Mopar 53032704AB (used in a 04-06 Jeep 4.7L HO). They have worked the best on my 49 PSI rail. However, they are EV6 connectors so you would need an adapter.The Bosch 0-280-155-703 (Neon) should work well given the specs as well. And its an EV1 plug. They are frequently used for stock replacements on 4.0Ls, and are a good fit in that application because their fuel pressure is 39psi. They should flow around 24 lbs in a 49 psi rail, making them a good fit for a stroker.