Jeep Strokers

I had new autolite app9... Whatever the number is for the wrangler

Cheromaniac wrote:

Black00Sahara wrote:Block was taken to .020" over and block and head both had .004" taken off in order to ensure they were perfectly flat.

Crank casting number is 3235477 OEM Jeep 4.2L crank

OEM Jeep 5.875" center to center connecting rods casting # 707

.020" over sized Speed Pro Coated Hyper. pistons (piston to wall clearance built into pistons) #p3071

.020" over speed pro factory replacement rings #s38816

Engine Tech camshaft #es242 .408" int/.414" exh lift, and duration @ .050 lift 188 int/190 exh

Felpro gasket set factory replacement. I don't have the head gasket part number anymore, but it is an OEM style kit.

The Compression Ration calculates to 10.2

It looks like you have a Melling stock replacement camshaft so the cam position sensor should already be properly synched if you used the toothpick method.
You've quoted an SCR of 10.2:1 but according to my calculations it's actually 9.7:1. That'll make the DCR pretty high with the cam that you're using.
You really need a wideband O2 sensor and gauge so you can find out what's really going on with the AFRs. My feeling is that your engine's running lean at the low rpm where the stock computer is locked into a 14.7:1 AFR at WOT. I somehow doubt that the injectors you bought were 27lb'ers so can you give us the part no. just to check?

I just found the reciept for the injectors. I got them from fuelinjectorconnection.com

It says-

1 x JEEP STROKER 27lb 4.0 Bosch III set of 6 (JEEB64)

It does give flow rate for each injector when they tested them and they are all at 280-282 cc/min

Thats it though. It doesn't have a brand or anything.

I drove it a bit today and after it warmed up it started pinging/detonating real bad. I brought it home and checked the camshaft position sensor to make sure I had it calibrated right, I did, it was spot on.

If I am running to large of injectors would it be doing this?

By reading and doing calculations my injectors should be around 246 cc/min (23.4 lbs/hr) and according to these injectors they are at 280-282 cc/min (26.7 lbs/hr) which is to much fuel?? Does that make any sense?

If the DCR is too high, having the engine run rich won't cure the pinging problem. We still need to see what's really going on with the AFR's at WOT from a wideband O2 sensor.

Have you checked the fuel pressure at the rail? Clogged fuel filter? weak/bad fuel pump?

CobraMarty wrote:Have you checked the fuel pressure at the rail? Clogged fuel filter? weak/bad fuel pump?

Fortunately Autozone has a fuel pressure rental kit. I got it yesterday and will check it tonight or tomorrow.

I will also have my mechanic run it on his computer and get a datalog of everything else.

CobraMarty wrote:Have you checked the fuel pressure at the rail? Clogged fuel filter? weak/bad fuel pump?

Fuel pressure was fine. Looks like 42.5 psi at the rail.

The pressure is a bit low. It should be 49.2psi plus or minus 2 psi. Minimum would be 47.2 psi. However, that may not be the issue.

Did you check the TPS and MAP sensors? O2 sensor(s)? Take a look at the magnet in the cap of the cam sensor as well. Make sure its not loose and still has decent magnetism.

When your mechanic hooks his scan tool up to it he should look at the short term and long term fuel trims, TPS, MAP, CTS and O2 sensor.

Black00Sahara wrote:

CobraMarty wrote:Have you checked the fuel pressure at the rail? Clogged fuel filter? weak/bad fuel pump?

Fuel pressure was fine. Looks like 42.5 psi at the rail.

What's the fuel pressure when you disconnect the vacuum line from the fuel pressure regulator? It should shoot up to at least 49 PSI. That's the important fuel pressure reading to know.

2000 TJ , IDK but I think that the TJ is like the XJ and have a returnless fuel system and the FP and FPR is in the tank. There is no vac hose to remove. The rail pressure at idle being 42 is troublesome. I wonder what it is when driving? A clogged fuel filter or a failing fuel pump will put out even lower rail pressure or not enough volume of fuel at speed. At idle it can be fine.

42 psi makes your 27 lb injectors really 25 lb'ers.

10.2:1 is high compression. Have you tried the highest octane gas you can buy and a couple cans of octane booster? 93 octane + 2 cans of octane booster should help it not to detonate if it is due to the high compression.

CobraMarty wrote:2000 TJ , IDK but I think that the TJ is like the XJ and have a returnless fuel system and the FP and FPR is in the tank. There is no vac hose to remove. The rail pressure at idle being 42 is troublesome. I wonder what it is when driving? A clogged fuel filter or a failing fuel pump will put out even lower rail pressure or not enough volume of fuel at speed. At idle it can be fine.

42 psi makes your 27 lb injectors really 25 lb'ers.

10.2:1 is high compression. Have you tried the highest octane gas you can buy and a couple cans of octane booster? 93 octane + 2 cans of octane booster should help it not to detonate if it is due to the high compression.

I run Shell 93, which is the highest we can get here. I tried octane boosters already, all they did was make my plugs orange.

I thought Stock is 43 lbs at the rail, so its right on?
The 25lbs is what I need anyway (well 24, but close), so thats ok.

A friend thinks the compression is just way to high, like maybe the machinist messed up and took to much off the head or block when finishing it up. He suggested testing the cylinder compression. When I asked how and he told me, I remembered the shop doing this when they built it and i think it was 235/ cylinder or something like that. When I told my friend that he nearly blew a gasket himself... He said "they messed up, it will never run pump gas on that."
I am going to rent the test tool from Autozone tonight and I will post the exact numbers this weekend.

Black00Sahara wrote:I thought Stock is 43 lbs at the rail, so its right on?
The 25lbs is what I need anyway (well 24, but close), so thats ok.

No, its 49.2psi plus or minus 2 psi. Minimum would be 47.2 psi. Did you test it while driving? A faulty pump could supply correct pressure and volume at idle, but not while the engine is under load.

i think it was 235/ cylinder or something like that.

If it is really that high it probably does have too much compression. Knowing what cam you are running would help too.

SilverXJ wrote:

Black00Sahara wrote:I thought Stock is 43 lbs at the rail, so its right on?
The 25lbs is what I need anyway (well 24, but close), so thats ok.

No, its 49.2psi plus or minus 2 psi. Minimum would be 47.2 psi. Did you test it while driving? A faulty pump could supply correct pressure and volume at idle, but not while the engine is under load.

i think it was 235/ cylinder or something like that.

If it is really that high it probably does have too much compression. Knowing what cam you are running would help too.

I didn't test it while driving but i guess it is a little low then. I need to change the filter (im sure its clogged). Its in the tank ... ugh

I am running this cam-
Engine Tech camshaft #es242 .408" int/.414" exh lift, and duration @ .050 lift 188 int/190 exh

Stock replacement camshaft. Could have used a cam with more duration and over lap to bleed off some of that pressure.

I have the compression test numbers.

#1 - 230
#2 - 228
#3 - 235
#4 - 230
#5 - 232
#6 - 235

So, I have been told with these numbers, this Jeep will NEVER run on pump gas. I would have to run C16 or C21 (race fuel).