BLUEFSEE

My '88 GXL N/A just started having an issue with a hard start after having an issue with overheating on me... I did the thermostat bypass(which after doing it the right way..ie: plugging the bypass hole in the housing..) it works great.. but all of a sudden, weeks after that mod, I am getting the very hard start issue(to the point of killing the battery).. after about 10 mins. or more of trying, it starts and runs as if only one plug was firing, while smoking up a storm.... then after a min. or so it will clear up and run perfectly... but shut it off, and within 20 seconds will do the same thing...fuel pressure at idle is around 30psi. and will rise to about 40psi. when under a load... is this normal or is my pump going out?... also when i shut the car off, the pressure immediately drops to zero.. and the pump only runs while starting the engine and of course while the engine is running, I am not getting the "prime" surge before start... would blown coolant seals cause hard starts?..or is that just a flooding issue?... is the fuel pressure normal for an N/A? one other thing I noticed was a hose at the fuel pump, that seems to run to a purge valve or something on the tank, is broken off... but I read that it is only to vent pressure off the tank, and it just goes to the charcoal tank.. i would think it is still ok..but IDK.. also, I get the left turn stall and I have checked the baffle and it is good.. and the pump I have has a big box looking filter instead of a sock, and it seems clean.. I checked the voltage at all the wire an I get 13+ volts at the red wire but the green wire is giving me fluctuations between 0 and 6 volts and is very erratic.. is that the tank level sender?

thanks in advance for any help I can get...

Lee Kelsoe
'88 FC GXL
air pump delete, electric fan, thermostat bypass, Racing Beat Cat-back Exhaust
Fender-mounted CAI

RotaryRocket88

iTrader: (7)

First off, you can find fuel pressure specs in the FSM. Links are in the FAQ or just go here: http://www.rotaryheads.com/PDF/2nd_gen/. Roughly 30 psi at idle (vacuum) and 40 psi under load (0 manifold pressure) is what it's supposed to be. The pump does not "prime" the system; it will only run when the key is turned to 'START' or the AFM door is being pulled by engine vacuum (running). But you should see pressure held after shutting the engine down. The specs are in the FSM, but you should only see a very slow drop in pressure. If not, you could have an external leak, or a leak inside the fuel tank/pump. An o-ring or fuel pump check valve could cause it.

Since you have the stalling problem while turning, replace the fuel pump sock (yes, OEM is squarish). It can look clean, but still be plugged.

The wire colors on the fuel pump plug (harness-side) are Blue (L), Black (B), White/Red (W/R) & White/Green (W/G) (FSM page 50-36). L is power and B is the ground. W/R is for the low-fuel sensor, and W/G is for the fuel level sender.

BLUEFSEE

thanks for all the info RotaryRocket88.. I have the FSM downloaded but couldn't understand the wiring diagram for the fuel pump very well..lol.. guess I need to take a day and read that thing...
yesterday I disconnected the battery for the day and after reconnecting it, it seemed to start better and eventually started to hold pressure after shut-down... today it was running much better and starting better, and held fuel pressure at around 25psi while at work.. but still stumbles really bad and smokes bad for a sec. at startup..
I'll replace the "sock" and look into replacing the injectors soon..
thanks again...

rdchaplin

you could also have leaking injector(s) hench fuel pressure goes to zero. I had an 88 TII had similar problem usually only when engine was warm. I sent all injectors to Marrin for rebuild, still did it. So I implimented the hot start solution and that worked; switch in fuel pump circuit. Turn off the pump, crsnk the engine then turn it back on and it starts fine.
Cheers, Doug