Hello, I installed a tpi fuel pump in my '92 TBI RS because my pump died, I had a complate gas tank from a '90 IROC with a new pump, and I was planning on switching to tpi in the future. I have read lots of posts from tbi guys that appear to be running higher pressure fuel pumps without problems so this is why I installed this pump. The problem I had is after driving for aprox 10 minutes my car started hesitating and bucking serverely and I noticed a gas smell. I popped the hood and found gas pouring out of the evap canister port that has a factory cap (pressure vent?) and I found gas pouring out of the line from the purge solenoid (mounted on the canister) when I disconnected it at the solenoid. I removed the gas cap and lots of pressure released and gas stopped pouring from the canister. I know that my hesitation problem was due to lots of raw fuel entering the tbi unit through the evap purge control solenoid line and every time I remove my gas cap, after the engine has been running, I have a lot more pressure exiting then before. I suspect that the excessive pressure from the tpi pump is causing these problems. Has anyone else had problems installing a tpi pump in a tbi car?

 

I am running a Bosch TPI pump in my TBI van tank with no problems. Perhaps you crossed the return/vapor lines on the tank when you put it back in. That would explain fuel being returned to the TBI through the Vapor lines.

 

I'm running a Master (cheap brand ) tpi pump and I haven't had any problems. I was worried when I installed my pump that I would cross the lines, that's why I took special care to mark them.

 

I have a walbro 255 and it was running OK. This sounds pretty possible.

 

Hi guys, Thank you very much for your responses. I checked today and the lines don't appear to be crossed (they appear to be all different sizes). I swapped the known good tank pressure vent from my old tbi gas tank and no change, problem still exists. My tank appears to be developing too much pressure. The car idles fine. I figured the excess pressure being returned from the regulator at the tbi unit could be causing this pressure build up. Tpi runs at 40psi or so I believe and tbi needs 15psi or so? This was my theory but all you guys seem to be runing these high pressure pumps with no problems so it must be something else I've done. Thank you again for you respones, and I'll have to check everything that I've done again.

 

Pumps won't make a bit a pressure without something blocking the flow, I.E. the regulator. All you would be getting with the TPI pump is more volume not pressure, the fuel pressure is determined by the regulator on the TBI unit.

Your vent line is either crushed somewhere or the evap valve is stuck closed. I had the same pressure building problem when my vent line got crushed while swaping a motor.

I can say with abosolute certainty that it's not the added volume of your pump causing your problem. A walbro 255 has more than double the volume of a stock TPI pump and no one has problems like yours with it.

 

Well, I rechecked my lines again and after looking a little closer I did find that I had swapped the fuel return line and the evap line at the tank. Opps! I was suprised on how easy that is to do. However my evap canister is still saturated with raw fuel from my mistake and therefore I'm still getting bad hesitation. At least it's no longer pouring fuel from the canister. I guest I'll probalbly have to replace the canister and maybe the vapor vac valve near the canister. Either way that's way easier than swapping a pump. Also I'll check my vent tube and make sure that I did not restrict it as I could have done that too. Thank you very much, you guys were right on!