Hard start problem. Need help please.

I'm having an issue with my project MJ. Let's start with its history first.

It's a 99 Cheromanche. I've pulled everything from my old 99 XJ and stuck it in this MJ.

In order to keep the fuel tank in the stock position, I swapped in the H.O. fuel rail, injectors, lines and pump.

The problem is whenever I try to start it; it takes about 5 times before it will fire up. Once it fires up, I have to work the gas pedal until the idle smoothes out or it will die. After about a minute of that, it will idle on its own and run fine. At this point I can kill it and start it back up with no problems. I just pulled and cleaned the throttle body and sensors on it, but it didn't seem to help. Any suggestions?

Thanks
Ben

You might have a bad temp sensor.

How about some more details on the morphing?

99 XJ into what year MJ?

jeeperjohn said:

You might have a bad temp sensor.

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Temp sensor doesn't come on-line until the engine reaches closed loop temperatures. Has no effect on starting.

Bucketheadben said:

... whenever I try to start it; it takes about 5 times before it will fire up. Once it fires up, I have to work the gas pedal until the idle smoothes out or it will die. After about a minute of that, it will idle on its own and run fine. ....

Click to expand...

If you are using the 1999 ECM/ECU engine computer, those are the common symptoms of a bad battery. Load test the battery, it may have enough power to start the engine, but the low battery voltage re-boots the ECU/PCM.

joe_peters said:

How about some more details on the morphing?

99 XJ into what year MJ?

Click to expand...

Everything is from the 99 except the fuel pump, rail, line, and injectors(all 94). The MJ was originaly a 89, but all that's left of it now is the body and frame.

Tim_MN said:

Temp sensor doesn't come on-line until the engine reaches closed loop temperatures. Has no effect on starting.



If you are using the 1999 ECM/ECU engine computer, those are the common symptoms of a bad battery. Load test the battery, it may have enough power to start the engine, but the low battery voltage re-boots the ECU/PCM.

Click to expand...

I did have to replace the battery a few weeks ago, but it still runs the same.

Ok, so the fuel pump, rail, line, and injectors are all from a system designed to operate at 30/31 psi with vacuum to the pressure regulator and at 39 psi w/o vacuum to the pressure regulator, and you are trying to operate a 99 vehicle with electronics wanting 49 psi constantly.

Right?

That is correct. I was told that the H.O. system would work fine. Here is the link to that topic. http://www.comancheclub.com/forums/viewtopic.php?f=2&t=14996
I really do appreciate the help trying to figure out the problem. This project has been sitting way to long.
Ben

You said you swapped injectors... the MJ ECU can't handle the 99 XJ injectors

Bucketheadben said:

That is correct. I was told that the H.O. system would work fine. Here is the link to that topic. http://www.comancheclub.com/forums/viewtopic.php?f=2&t=14996
I really do appreciate the help trying to figure out the problem. This project has been sitting way to long.
Ben

Click to expand...

Well, there is HO and then there is HO--specifically, OBDI 91-95 and OBDII 96-01.

The fuel pressure for the OBDI was the same as the Renix, with pressures I already posted above. The OBDII PCM and CAM sensor (which provides the PCM input for the firing duration of the injectors) were designed to operate with different pressures. The PCM, based on inputs from the CPS/CKP and CAM sensor, is trying to operate based on certain programmed parameters, but some of the hardware doesn't match, and I think that is the root of your problem.

However, I might just be p/ing into the wind.