HELP!!? 87 RENIX 4.0 long crank/long start
CF Veteran
Joined: Aug 2011
Posts: 10,489
Likes: 24
From: Nor-Cal Coast
Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
You watch the pressure after shutdown. Is it dropping off fast? Then squeeze the soft return line off and see if it still drops fast.
Most guys would just live with the "poor mans prime" until it's time for a new pump. And again it's true, in my case the premium Chevron gas cured mine. Not sure if it was the injectors or the check valve. (FPR is pretty rare I think). Kemtool or BK-44 just might do the trick as well.
Most guys would just live with the "poor mans prime" until it's time for a new pump. And again it's true, in my case the premium Chevron gas cured mine. Not sure if it was the injectors or the check valve. (FPR is pretty rare I think). Kemtool or BK-44 just might do the trick as well.
CF Veteran
Joined: Aug 2011
Posts: 10,489
Likes: 24
From: Nor-Cal Coast
Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
I wouldn't. BK 44 is the real deal I gather but I don't know where to get it. Likewise Kem-tool in the can with a screw top. I've never used it as an additive but I think there are directions on the can. It for sure cut's crud. Or heck, try the Chevron Premium with Techron. Like I said I was surprised, I didn't expect that to do anything, but it did!
CF Veteran
Joined: Jan 2015
Posts: 1,508
Likes: 5
From: Oregon Coast
Year: 1999
Model: Cherokee
Engine: 4.0L I6
I wouldn't. BK 44 is the real deal I gather but I don't know where to get it. Likewise Kem-tool in the can with a screw top. I've never used it as an additive but I think there are directions on the can. It for sure cut's crud. Or heck, try the Chevron Premium with Techron. Like I said I was surprised, I didn't expect that to do anything, but it did!
CF Veteran
Joined: Aug 2011
Posts: 10,489
Likes: 24
From: Nor-Cal Coast
Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
Yea, just happens it was the premium that I actually saw work.
Mat, I just now watched your vid. Jesus! First, if you do the poor man's prime, does it start allot faster? (Renix always takes a sec).
Second..be aware the top left post in this pic provides power to the pump while it's cranking. In your case I might just check that. (that is your starter relay there by the battery)
Mat, I just now watched your vid. Jesus! First, if you do the poor man's prime, does it start allot faster? (Renix always takes a sec).
Second..be aware the top left post in this pic provides power to the pump while it's cranking. In your case I might just check that. (that is your starter relay there by the battery)
CF Veteran
Joined: Jan 2015
Posts: 1,508
Likes: 5
From: Oregon Coast
Year: 1999
Model: Cherokee
Engine: 4.0L I6
I wouldn't. BK 44 is the real deal I gather but I don't know where to get it. Likewise Kem-tool in the can with a screw top. I've never used it as an additive but I think there are directions on the can. It for sure cut's crud. Or heck, try the Chevron Premium with Techron. Like I said I was surprised, I didn't expect that to do anything, but it did!
Senior Member

Joined: May 2012
Posts: 925
Likes: 5
From: Fort Erie, CANADA
Year: 1987
Model: Cherokee
Engine: 4.0
Put more gas in it first before messing around. You can't run properly on additives. The FPR is checked by taking off the vacuum line and seeing if the pressure goes from 31 to 39 psi while engine is running. If you have the gauge on the rail, you'll see that happen. You need to go through Cruisers RENIX tips or people get cranky!
Thread Starter
Seasoned Member
Joined: Jul 2012
Posts: 312
Likes: 0
From: Little Elm, TX
Year: 1987
Model: Cherokee
Engine: Inline 6 cylinder
I meant I'll put seafoam in it when I get gas. And the FPR is working right then. I already checked it. I've gone through his tips multiple times.
Senior Member

Joined: May 2012
Posts: 925
Likes: 5
From: Fort Erie, CANADA
Year: 1987
Model: Cherokee
Engine: 4.0
OK-Post back after you get gas in the tank. Kind of pointless to keep looking for ideas until you try the basics first. If you've done Cruiser's tips, like grounds, CPS voltage checks, TPS calibration etc, then you have done it all.
Thread Starter
Seasoned Member
Joined: Jul 2012
Posts: 312
Likes: 0
From: Little Elm, TX
Year: 1987
Model: Cherokee
Engine: Inline 6 cylinder
Yep, I've upgraded the grounds with like 2 gauge wire. I've checked the CPS voltage at the ECU connector. I should probably check the TPS again though.
Tomorrow, I will get like $25-$30 in gas and see if that helps. Then when the check valve comes in, I will install that and see if it helps. Thanks for all the help guys. I appreciate it.
Tomorrow, I will get like $25-$30 in gas and see if that helps. Then when the check valve comes in, I will install that and see if it helps. Thanks for all the help guys. I appreciate it.
Last edited by matt0106; Aug 18, 2015 at 10:33 PM.
Thread Starter
Seasoned Member
Joined: Jul 2012
Posts: 312
Likes: 0
From: Little Elm, TX
Year: 1987
Model: Cherokee
Engine: Inline 6 cylinder
Yep, I've upgraded the grounds with like 2 gauge wire. I've checked the CPS voltage at the ECU connector. I should probably check the TPS again though.
Tomorrow, I will get like $25-$30 in gas and see if that helps. Then when the check valve comes in, I will install that and see if it helps. Thanks for all the help guys. I appreciate it.
Tomorrow, I will get like $25-$30 in gas and see if that helps. Then when the check valve comes in, I will install that and see if it helps. Thanks for all the help guys. I appreciate it.
Senior Member

Joined: May 2012
Posts: 925
Likes: 5
From: Fort Erie, CANADA
Year: 1987
Model: Cherokee
Engine: 4.0
More likely too LEAN (if fuel issue). Could be fuel pump on the way out. Could be bad TPS (if sluggish when running). Won't know until you put gas in as said a few times before. No point speculating further.
Thread Starter
Seasoned Member
Joined: Jul 2012
Posts: 312
Likes: 0
From: Little Elm, TX
Year: 1987
Model: Cherokee
Engine: Inline 6 cylinder
Getting gas didn't seem to help. Fuel smell while cranking, something could be leaking? ALWAYS starts, just takes FOREVER. Also, coolant level keeps getting lower. No signs of any head problems.
Not sure what is happening. But, I'm going to replace the fuel filter and see if that helps.
Not sure what is happening. But, I'm going to replace the fuel filter and see if that helps.


