Engine 84 CJ7 issue finding correct fuel pump.
Hey everyone, first time posting here. I have a 84 CJ7 with the 4.2 I6, previous owner installed the Mopar fuel injection kit that is basically just a 1994 wrangler system(at least that is what the manual says). Both the previous owner and I have had issues with the engine randomly cutting out, for me it only happened when the engine would be fully warmed up, and usually a pretty hot day. If I remember correctly the previous owner would drive somewhere, park, and when he would come back out the Jeep would not start(he would have to wait about an hour and then it would start, he thought it was vapor lock). In my experience with this Jeep that has never happened. The only issues I have had is that I will come to a stop, and when I start accelerating again the engine will fall on its face, sometimes stall, but would always restart and when I give it enough throttle it would smooth out, and I can continue on my way.
So moving on, I started diagnosing the issue, my first thought was a fueling issue, so I hooked a gauge up and drove around with it taped to the windshield. (mind you I don't drive the thing much, couple hundred miles a year probably). The first 5-6 times I drove it it never acted up(of course). The last time I drove it, I was sitting in a drive through or something, and I watched the fuel pressure drop from about 60 psi, slowly down to about 20 psi. If I gave it gas the pressure would come back up, but then fall again. I have always been a little suspect of the fuel pump, it sounded kind of odd to me. So I ordered a replacement pump, specifically the HESHFP90, I found this pump doing some searching with google, and it led me to a forum(might have been this one I wasn't really paying attention to what website it was, but the guy who recommended it seemed pretty knowledgeable about this sort of thing.) I cant remember if I saw the specs in the manual or if it is from the forum that I am thinking of, but this system is supposed to run at 31-40 psi. I installed the new pump tonight, and a new fuel pressure regulator, I kind of thought this could also be the issue seeing as revving the engine would bring fuel pressure up. With the gauge still installed, it is a 100 psi gauge, and it pegged the thing. When I would rev it the pressure would drop off the peg, but still would be over 100psi. I looked back to see if i got the right pump sent to me, and its definitely the one i was supposed to get. the website I bought it off of even lists it as the replacement pump for this kit, ill try to add the link if I can.
https://hesco.us/products/21873/jee...0/hi-pressure-fuel-pump-heshfp90#.X1GCOnlKguV
I let the engine run just to see what would happen, after about 20 seconds the fuel pressure started dropping, all the way to 10 psi and the engine would stall, I can restart it and it will peg the gauge again, and then pressure drops. This would not happen with the old pump at all, it would stay at a constant 50-60 psi, which I realize is too high still, but closer than this! The only thing I have changed in the system is the fuel pump, and I added an inline check valve. (previous pump had check valve built into outlet). I also replaced all of the rubber hoses that I touched.
Might be worth adding when the pressure drops I can hear the pump whining like it is being starved of fuel.
Does anyone have experience with this? Thanks for any info!
So moving on, I started diagnosing the issue, my first thought was a fueling issue, so I hooked a gauge up and drove around with it taped to the windshield. (mind you I don't drive the thing much, couple hundred miles a year probably). The first 5-6 times I drove it it never acted up(of course). The last time I drove it, I was sitting in a drive through or something, and I watched the fuel pressure drop from about 60 psi, slowly down to about 20 psi. If I gave it gas the pressure would come back up, but then fall again. I have always been a little suspect of the fuel pump, it sounded kind of odd to me. So I ordered a replacement pump, specifically the HESHFP90, I found this pump doing some searching with google, and it led me to a forum(might have been this one I wasn't really paying attention to what website it was, but the guy who recommended it seemed pretty knowledgeable about this sort of thing.) I cant remember if I saw the specs in the manual or if it is from the forum that I am thinking of, but this system is supposed to run at 31-40 psi. I installed the new pump tonight, and a new fuel pressure regulator, I kind of thought this could also be the issue seeing as revving the engine would bring fuel pressure up. With the gauge still installed, it is a 100 psi gauge, and it pegged the thing. When I would rev it the pressure would drop off the peg, but still would be over 100psi. I looked back to see if i got the right pump sent to me, and its definitely the one i was supposed to get. the website I bought it off of even lists it as the replacement pump for this kit, ill try to add the link if I can.
https://hesco.us/products/21873/jee...0/hi-pressure-fuel-pump-heshfp90#.X1GCOnlKguV
I let the engine run just to see what would happen, after about 20 seconds the fuel pressure started dropping, all the way to 10 psi and the engine would stall, I can restart it and it will peg the gauge again, and then pressure drops. This would not happen with the old pump at all, it would stay at a constant 50-60 psi, which I realize is too high still, but closer than this! The only thing I have changed in the system is the fuel pump, and I added an inline check valve. (previous pump had check valve built into outlet). I also replaced all of the rubber hoses that I touched.
Might be worth adding when the pressure drops I can hear the pump whining like it is being starved of fuel.
Does anyone have experience with this? Thanks for any info!
