mlevario99

I installed a L59 flex fuel engine out of a 04 Tahoe (4x4) into a 78 CJ7 jeep (I am not using or plan to use flex gas, just regular gas). This was done a while back, it run fine for a while, had to replace the exterior inline pump to an in-tank fuel pump, walbro 255 I believe. Lately, I have had some issues when I took the jeep for a drive and I step on the gas, it felt like the engine was not getting enough gas. I checked the fuel pressure, I was getting like 40 psi to 42 psi with key on, and about the same with engine running, but if I step on the gas, the pressure drops and stays there, is starving for gas.
-what is the pressure needed with the key on, and the engine running, I understand I need to unplug the vacuum from the pressure regulator.
-do I need a bigger pump because of the flex-fuel injectors?
-If I am not using any flex-fuel can I disable the flex-fuel in the computer?
-can the pressure regulator be the problem?
thanks for your help

Jimbo1367

What lines are using? I would NOT disabled flex fuel. No need to. The pump should be way more than enough. Where did u get the fuel pump? It could be a nock off pump.

mlevario99

I am using 6 AN. The fuel pump I bought it from Summit, is a walbro, I might have to install another one that I have just to check the pressure.
thanks

rpturbo

iTrader: (47)

If your using a stock truck fuel rail, fuel pressure should be 58#.

ls1nova71

iTrader: (4)

If it's flex fuel with the regulator on the fuel rail, it should be around 45psi. The non flex engines are the ones that run at 58psi.

mlevario99

The 45 psi are measure key on engine not running, or engine running, vacuum hose into the regulator disconnected?

Jimbo1367

Good to know. I always thought it was 58

68Formula

• Keyed on, not running: 58psi
• Idle with vacuum connected: ~45psi (should = 58 psi - engine vacuum at idle)
• Running with vacuum disconnected: 58psi

Check your fuel filter lately?

gagliano7

I had a similar situation back when i first did my swap and the hose on the pump in the tank came loose and i was reading 36 psi. Just something to think about.

mlevario99

I install a new walbro pump, key on not running pressure is 52 psi, engine running vacuum line unplug, it reads 52 psi, if I plug the vacuum it reads 42 psi. Took the jeep for a ride, but when you try to step on the gas, is starving for gas, it just looses power. Not sure what else to do, other than getting another pump.

question, can the filter cause the fuel pressure to drop, I have one of those AN filters, that has a round screen inside, can the screen be installed the wrong way that it causes fuel pressures problems?

thanks

Jimbo1367

It is possible for the filter to restrict flow. I would be more worried if it’s a “off brand”. It wouldn’t hurt to make sure it’s ok. Inspect it.

mlevario99

I rotate the filter and it work, took it for a ride and had no issues