88 FC requires pump prime to start
 

Hello all, I recently purchased an 88 FC with a rebuilt engine and transmission from Seattle area, and I've been greeted with numerous small problems to fix.

One of the problems I'm having is that it won't start immediately due to no fuel at the injectors. I phoned the previous owner and he told me that he had been starting by keying on/off repeatedly to get the fuel pump running, re-prime the lines, and get fuel back up to the injectors. Every time I leave the car for longer than about 10 minutes it seems to have the same problem. As best as I can tell, fuel is draining back to the tank every time. So, what would cause this condition? It's getting a little old sitting in my car keying on/off for 10 minutes every time I want to drive anywhere.

The pressure regulator seems to be fine. I've checked the top 2 injectors, but I wasn't ready to tear apart all the EGR stuff to get to the lower injectors. What's most likely? A hole in the lines somewhere? It seems to me that would leak fuel everywhere, and I'm not seeing a fuel leak anywhere.

The fuel pump does not run with the key in the 'ON' position unless the AFM door is propped open or the fuel pump test connector (yellow plug on passenger strut tower) is jumped. If neither of these are done, the system will not "prime". It doesn't need to.

What happens when you try to start it? It cranks, but does not not ever start? Does it do this when cold and when warm? Or just under one condition?

I can hear the fuel pump running when I key on, so I think it's going...

It cranks and no start, no sign of starting at all. It has happened everytime I've tried to start it.

However, it will start if I sit in the car and key on/key off repeatedly, again for like 10 minutes. Worth mentioning that I repeat trying to start during that time, sometimes it'll try to start for a second but fail. After keying on/off for a bit longer it'll start.

RR88 is correct, fuel pump doesn't turn on till cranking/running.

Possibly check for a leaking pulsation dampener and/or smell for gas under the hood during or after it was running. [edit: which sounds like you may already have]

Possibly Flooding?? You can unplug the fuel pump, just behind the drivers side rear strut tower, crank, plug it back in and try to start...

If it is actually running, someone has done some re-wiring. The first place to check would be the yellow test connector I mentioned. If it has a piece of wire connecting the two sides, remove it, then see how the car behaves.

I would also suggest testing fuel pressure. A gauge can be tee'd into the feed line to check pressure during operation. The system should also hold pressure for a long while after shut down.

I'll check for leaking under the hood. Could it be flooding if it's not starting after sitting overnight? I was under the impression that that stops being a problem after you let it sit for awhile, but maybe I'm not understanding the mechanics of it right.

I'll check both those, the previous owner definitely did some weird wiring stuff to the car so I wouldn't put it past him.

I had a failed o-ring inside my tank that caused a similar issue.

I'd have to bump the starter to get the pump moving then crank as normal.

The o-ring would basically leak pressure off in the tank, so when I'd try and start without bumping it, it took several second longer because the pump was having to struggle to build pressure.

ok, looks like there was in fact a jumper line in that yellow check connector, so that at least explains why the pump was running in the 'on' position.

I pulled it out and tried to start with no success, put the jumper back in, did the usual procedure, and got it started. Once it had been running for a few minutes I pulled the jumper out and drove around a bit. I stopped for a few errands with the car off for a few minutes each time, and was able to get the car running again each time, but a little slowly.

Just ate dinner and the car was sitting for about 40 minutes, tried to start it, no luck. So there's something else going on with the line. It could be the o-ring jjwalker mentioned or a similar problem with pressure.

after 'bumping' the starter and leaving the car with key 'on' for a few minutes, it started right up. So, pressure loss somewhere then?

Most likely. If there is no external gas leaking, I'd go looking inside the tank at the fuel pump assembly.

Do you guys think it might help to switch the pump? I have a parts car I can swap a pump from.

I'm not sure where the pressure leak is occurring, but it seems to be interior (not smelling or seeing gas anywhere external). jjwalker, where was the o-ring that failed on your car?

sounds like a fuel pump to me. naturally the pump will bleed most of the pressure off back into the tank, but keep fuel in the lines from the tank to the rails. it sounds as if the fuel rails are draining back into the tank past the pump. i've not seen a way to rebuild the pumps, and a new one is cheap enough anyways.

This was years ago, but on the outlet side of the pump toward the engine.

Alright, the plot thickens:

after I got the 'bump the starter' solution to work, I went over to a friend's house, stayed the night, got up in the morning to start it, and after 15 minutes of alternately trying to start and waiting for the pump to pressurize, still no luck (though the engine occasionally showed very weak signs of trying to catch... frustrating) and I was forced to leave the car for the day and bum a ride to work. At this point I'm assuming that the seal has degraded to the point that the pump can't build pressure at all, and I started planning to swap the pump as soon as possible.

Got a ride back to the car on the off chance that I'd be able to start it up, flicked the starter to get the pump started, and to my shock the car started right up as if it didn't even have to try. This makes no sense to me if we're assuming the pump can't hold pressure in the system, as the pump wasn't running for even an instant before it started right up after sitting all day.

Since then, I've driven it home and after trying to start it twice it has repeatedly not started. I'm very puzzled by the one time it did start, and now it doesn't seem interested again. I can still swap the pumps, but it seems to me that there's something else going on... A seal wouldn't randomly decide to hold pressure again, would it? Seems more likely to be a bad electrical connection somewhere?

Could certainly be electrical... and at this age, our cars are getting extreme gremlins in that department. It could be the relay under the dash. But start with the pump since you planned that anyway.

so the symptoms is the car wont start without turning the pump off first and then back on after the engine catches?

if so, check engine compression, fuel pressure, and vacuum.

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