3.4 swap into 1985 Jeep Cherokee questions?

[bszopi]

You should have looked for the plugs inside the cabin to see where they plug in. Might have been useful.

[cardana24]

You should have looked for the plugs inside the cabin to see where they plug in. Might have been useful.

It was over 100 degrees, the car did not have carpet and the sun was beaming through the windshield...it was just a little bit hot to be laying down in the floor board to see where the wires went under the dash. But, I agree...it may have been helpful.

[cardana24]

I am still getting the crank but no run...when it starts to sputter and die, when I press the gas it has no effect on keeping it alive. I changed my plugs because they all had gas on them...still nothing. Does anyone know if I can test my VATS bypass with my test meter? What should I be reading on the out put? I want to rule that out. Any ideas or info is appreciated.

Also can someone please recomend a fuel pressure tester that will fit the threaded valve on the 3.4 rail. The Actron one that I picked up at advanced does not have an adaptor to fit that style...therefor I know I have pressure on the rail but I am not sure of the exact reading.

[pocket-rocket]

If the VATS was engaged, I don't think you would have any fuel being shot out of the injectors. And as for the pressure tester, I believe they sell two styles.

1. Does fuel and vacuum
2. Does fuel only and reads higher pressure then the one w/ vac. reading.

[cardana24]

If the VATS was engaged, I don't think you would have any fuel being shot out of the injectors. And as for the pressure tester, I believe they sell two styles.

1. Does fuel and vacuum
2. Does fuel only and reads higher pressure then the one w/ vac. reading.

From my understanding it will cut the fuel after about 2 or 3 seconds, but it will get the initial fuel from the pump priming.

Do you have a link to the fuel pressure gague that will fit our port?

[pocket-rocket]

I don't have a car with VATS on it, so you could be right. I believe the ones with VATS won't allow the starter to turn either, but you probably ran the ignition switch right to the starter, bypassing the VATS on that part. Here is a link to one that I found on Advances web site, but it isn't the same one I have seen in the store. If you go in there and tell them you need the one for fuel injection, they should be able to point you at the right tester. This one runs $40 on their site, and I believe the one in the store runs about the same.

http://www.partsamerica.com/ProductDetail.aspx?MfrCode=EQU&MfrPartNumber=3640&CategoryCode=3390

The one you have has no threaded parts on it, right? You just push it on over the hose going up to the carb, correct? I have had that one before as well. The one for fuel injection does indeed have threaded adapters to open the schrader valve in the fuel rail to get the pressure reading.

This is the description on the one I linked to:

* Large, easy-to-read 2-1/2" dial face with 0-100 PSI scale
* Durable 16" gauge hose and 6-foot bleed-off hose with solid brass fittings
* Includes Ford, GM and Chrysler test adapters and a "Tee" adapter for import vehicles
* Helps identify and diagnose low fuel pressure, a faulty fuel pressure regulator, leaking injector(s), fuel leaks and/or clogged fuel filters.

[cardana24]

I don't have a car with VATS on it, so you could be right. I believe the ones with VATS won't allow the starter to turn either, but you probably ran the ignition switch right to the starter, bypassing the VATS on that part. Here is a link to one that I found on Advances web site, but it isn't the same one I have seen in the store. If you go in there and tell them you need the one for fuel injection, they should be able to point you at the right tester. This one runs $40 on their site, and I believe the one in the store runs about the same.

http://www.partsamerica.com/ProductDetail.aspx?MfrCode=EQU&MfrPartNumber=3640&CategoryCode=3390

The one you have has no threaded parts on it, right? You just push it on over the hose going up to the carb, correct? I have had that one before as well. The one for fuel injection does indeed have threaded adapters to open the schrader valve in the fuel rail to get the pressure reading.

This is the description on the one I linked to:

Yeah that one looks like it will work. I may check to see if they have it in stock.

[pocket-rocket]

It wont be the same brand, but it will still be a fuel injection one for sure. I think Advance sells Actron?

[cardana24]

Advanced told me they could not get the one I wanted, so I ordered it at AutoZone. It was 40 bucks it says that it should work on GM MPFI vehicles up to 96.

[cardana24]

I'll be able to pick up my fuel pressure tester today, but while I am waiting on getting that I have a question. Could my symptoms point to low fuel pressure? Would my engine not start if the fuel pressure was down by about 10 PSI? I know the camaro 3.4 is designed to run in the mid 40's on fuel pressure, and I am doing some reading about the the fuel pump that I am using http://www.lunghd.com/Tech_Articles/...iagnostics.htm

and I am not sure what the 88 Cherokee 4.0 is rated for but it looks like in this article the guy is saying that you should only see mid 30's on fuel pressure. Could this possibly cause my issues?

[Canyonero]

Depends, is that reading of 30psi before or after the FPR?

With my fuel pump from a 2.6L Isuzu 4cyl, I'm getting 45psi at the rail on the 3.4L. I guess I'm not sure if the test port is before or after the FPR though.

[geoffinbc]

You always test before the regulator. Anywhere on the supply side, including the line. Anything after the regulator on the return side will have zero pressure, it is just a drain back to the tank.

[cardana24]

at the test port I am getting 40 psi with the key switched on. I have not tried starting it yet, but is this going to cause a problem?

[ssterlingb]

At or below 41 will cause it to run lean, but you have to cycle the switch a couple of times to bring it up to full pressure before you take your reading. It only runs a couple of seconds to prime the rail before it detects the engine started, and runs the pump after it starts. I am wondering if your not getting the pump running after it starts and only getting it during the initial priming. If you can hook up your meter or test light to the pump & see if you have power while it is running. The VATS can only be tested with an Ocilloscope. It gives a pulsed ground to the PCM. If it is continuous, or no ground at all, the PCM won't run. A little more advanced than what I can advise on.

[ssterlingb]

BTW, I sent you a diagram for the data port in that email. It should be on page one, the MIL lamp diagram.