Fuel pump won't stop priming, engine won't start (3FE) (1 Viewer)

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My rig is a 1991 with the 3FE.

I just finished replacing the head gasket. I put everything back together, and now I can't get it to start. Whenever the ignition is on, the fuel pump runs constantly instead of just for a moment to prime the lines. It will run as long as I leave the key on - I've let it go for several minutes. There is a loud hissing noise coming from somewhere in the vicinity of the fuel rail. Using a stethoscope, it seems loudest at the FPR. I'm guessing this noise is just fuel running through the lines - but if the engine isn't running, where is the fuel going? There are no leaks, as far as I can tell. If I try to start the engine it will crank and fire, but it won't start - it just sputters.

I have taken the fuel rail back out, cleaned it thoroughly, cleaned the injectors, and put new o-rings and seals on the injectors. I have double and triple checked all my fuel, vacuum and electrical connections. (Doesn't mean I still couldn't have missed something, but I've gone over everything I can think of multiple times.) I had just replaced the fuel filter before the head gasket blew.

I tried looking for a fuel pump relay to see if it was stuck, but apparently the 3FE doesn't have one?

Anyone have any ideas? I'd appreciate any suggestions, or any insight into the details of how the fuel system is controlled.
 
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Head gasket on a 3FE? Was it a severe overheat?

The fuel pump on a 3FE does not "prime" the rail.
The fuel pump relay is called the "circuit opening relay" and lives in the left kick panel.
That relay has 2 coils that fire the fuel pump at different times.
The primary coil fires when you crank the starter motor.
The secondary fires when the flap in the AFM opens as the motor begins to suck air.

If your fuel pump is firing with the key in the ON position, then it's possible that the AFM flap is stuck open.
I would try removing the connector on the AFM.
DO NOT REMOVE THE 2 PHILLIPS SCREWS ON THE HOUSING. THIS WILL DAMAGE THE AFM.
There is a thin spring clip on the connector that pushes up to separate the halves.

If that doesn't work, we need to look into the fuel pump logic and see what's going on.
 
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@jonheld

I unplugged the AFM, and the fuel pump stopped running. I removed the AFM to check the gate, and it seems to be swinging freely. It will stay in whatever position I put it. The pins and connector look fine, no bends or breaks.

A few years ago I disassembled the AFM to fix a broken connection (caused by removing those two screws). I soldered the connections back together and sealed the box up with silicone, and it hasn't given me any trouble since. It has been sitting on a shelf in my garage while I worked on the head gasket - no opportunity for damage, as far as I know.

The head gasket failed between the combustion chamber and coolant channel, causing my radiator to blow out. I don't know how severe the overheating was, but it was sudden, as I was climbing a hill. A couple days after this, I ran the engine long enough to move the rig from the trailer into the garage, and it didn't have any trouble. I took the head in to be milled; the machinist said it was pretty warped, but he was able to make it flat. This is the second time the head gasket has failed; the first time I was too lazy to get the head milled, which is probably why it happened again. I suspect both failures had something to do with a malfunctioning EGR causing the engine to run rich at times. I finally resolved that problem about a week before the second HG failure.
 
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I haven't checked for spark - it will fire, but not run. It just coughs and dies. I suppose I could have spark on some cylinders and not others.
 
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I removed the AFM to check the gate, and it seems to be swinging freely. It will stay in whatever position I put it.
That's NOT correct. It should want to gently swing closed with no air flow with the return spring. If the return spring is not able to close the flap, then the fuel pump will never shut off, and the ECU will never get an accurate reading of air flow. It will never run correctly in this condition.
 
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That's NOT correct. It should want to gently swing closed with no air flow with the return spring. If the return spring is not able to close the flap, then the fuel pump will never shut off, and the ECU will never get an accurate reading of air flow. It will never run correctly in this condition.

Yep, that didn't seem right to me either. I'll mess with it some more after breakfast and see if I can figure out what's wrong with it. Maybe the hinge just needs some lubrication?
 
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I didn't remove the distributor or any part of the ignition system, besides spark plugs. I did double check that the wires were going to the correct plugs.
 
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Yep, that didn't seem right to me either. I'll mess with it some more after breakfast and see if I can figure out what's wrong with it. Maybe the hinge just needs some lubrication?
The flap is supposed to move with air flow. You should be able to blow on it to make it move. I have never heard of ever lubricating that. It seems like the wrong idea to me.
 
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I would seriously be considering a replacement AFM at this point. Any 3FE equipped Land Cruiser (FJ62 or FJ80) will work.
There are also threads on here regarding a replacement from a specific Camry that work as well.
 
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If it's supposed to move that easily, wouldn't lubricating it help? I don't follow on why that would be a bad idea? Unless I used a type of lube that would be bad for the sensors or rubber hose.

I've been wanting to do an MAF replacement for a long time. Splitsec has (or had) a kit for it, but it's no longer on their website and they haven't replied to my emails asking if it's still available.

I've been trying to do anything I can to help my 3FE breath easier and run to its full potential. Looking at this AFM, it really seems like a horrible bottleneck for air flow.

Never heard of using an AFM from a Camry, that's interesting.
 
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Honestly, I have never dissected an AFM to examine the hinge points. I know there is a return spring under the top cap that is adjustable, and some folks have played games with it.
Personally, I feel that the AFM system works well, considering that the ECU was designed in 1986. There's really a limit to how much improvement you're gong to get on a 155 HP engine with 1st generation fuel injection.
It will never be a rocket, but if you follow the FSM recommendations for valve adjustment and periodic maintenance, it will be very reliable. Just like the tractor motor that it is.
 
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Well, I opened up the AFM to take a look. The gate is moving more freely as I work it back and forth, and it will now return to the closed position on its own. It may have just gotten stiff from sitting so long. But it's definitely not loose enough to open by blowing on it. As far as I can recall, it never has been.

Here are some pics of the inside.
IMG_7325.JPEG
IMG_7326.JPEG
IMG_7328.JPEG
 
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Joined
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Well, the gate is moving freely, and it returns to the closed position on its own. I didn't add any lube to the hinge. I plugged the connector back in, and turned the key to the on position - fuel pump does not come on! I put the AFM back together and I'm going to let the silicone dry for an hour or so before attempting to start the engine.
 
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