Dirt + water in gas, killed my idle

[Konyak]

I have an 89 GL 1800 4WD with the Hitachi carb, not SPFI, no computers, the only thing automatic is the choke. I have spent the last 2 hours reading through the results of searches, but everyone has SPFI or Turbo or something I can't compare with.

 

I broke the basic rule of letting my engine suck my tank dry the other day. Before I did this, it was running as well as can be expected, allthough it does stall coming out of idle under acceleration.

Anyway, after I refuled it, it started to die when I took the foot of the pedal. I'd had this happen before, and then I cured it by installing a fuel filter right up against the carb, as I knew the tank was rusty.

So I replaced both my fuel filters, but it still won't idle once the engine heats up.

 

Sum up:

1. Starts great when cold.

2. Auto-choke has it running at 2000 rpm or so, and if I don't do anything, it will slowly increase the rpm's to about 3500 ( ) and then the choke will turn off by itself.

3. After driving for about 15 minutes I'd say, something happens, I can feel it when it kicks in, and it doesn't run quite as smoothly. At that point, I know that if I lift off the gas pedal, it will quit. Time to do the handbrake-gas-pedal dance.

4. It comes and goes on it's own and sometimes, it seems to happen as a result of going over a speedbump a bit hard. (for instance)

 

What I've done so far:

1. Switch carbs, no difference.

2. Increased the idle stop screw. Anymore wouldn't be considered idling

3. Changed fuel-filters. I have two, both had rust deposits and water in them.

4. Put anti-condenser anti-freeze additive into the gas, cause of the water.

5. Car has Jacobs 8.0 mm super-duper sparkplug wires, pretty new plugs-rotor-distycap.

 

Any help is greatly appreciated. Feel free to use your abbreviations for various engine components, as often as you like, if only at first you use the un-abbreviated name I'm not familiar with all the English abbreviations, as it's not my 1st language.

To those of you who can't help out, but took the time to read this, perhaps with similar problems, hope this thread may help you out as well.

Have a Merry Christmas!

 

Thanks,

Konyak

[Prospeeder]

possibly killed the fuel pump or somthing, granted those have electronic fuel pumps. if you could get a spare, switch them out and see

[NoahDL88]

I don't know what kind of spark plugs you're using, but if you're using bosch plugs that could be one of your issues, NGK's are the ones you should use, and there pretty cheap too.

 

run some intake cleaner through a vacuume line, if a new carb didn't help then it might be real dirty inside the intake. its a long shot, but who knows.

 

if it works well until the choke comes off, you may have a problem with the idle screw, or the screw itself might be the wrong one. also make sure that your distributor is timed right and that it's vacuume line is going to the ported vacuume on the carb.

[desertsubaru]

Hicrappy carbs are known to do that. Mine did it to often and never really did find a cause. Most likely you got some dirt in the carb. I know that was one of my problems. Try running some cleaner or seafoam in the tank and see if that helps. If not then a rebuild or a weber is the next step. Put some dry gas in the tank for the water.

[GeneralDisorder]

Sounds like the idle circuit on the carb(s) is plugged or sucking air. This is pretty common on the Hitachi. The gasket between the upper and lower section of the carb is usually pretty rotten.

 

GD

[Konyak]

Ok, thanks for the help. It's running again, and here's what I did:

 

Even though I'd swapped the carb for another Hitachi some while back, I did it again this time, and it ran fine. However, after a week or so, it fouled up again, so I decided to take a look in the fuel tank. Removing it was harder than the crappy Haynes manual implied, but once out, I shook all the water and dirt out of it.

Planned to have it coated on the inside, but it was going to cost more than I could afford (Christmas:) ) so I swirled it out well, and put it back in.

Then I decided to check the fuel pump, as it was little more than a rusty chunk, and after hooking it up to some 12v on the bench, I couldn't get it to pump gas at all.

Since the pump wasn't working, I began to wonder if it was possible that the car had been sucking gas out of the tank using the return pipe from the carb ??? I'm sure there has to be a one way valve on that pipe, but it would sure explain how the carb managed to get so much dirt in it through 2 inline filters on the gas line.

Anyway, I bought a new gas pump, a generic American one that was probably intended to feed some much larger engine, I think with 8.8 psi pressure. It fit, and it worked, so I was a happy camper, feeling the car had more power now than before.

Until a week later, when it simply quit without warning. This time it wouldn't run at all, but if I squirted gas into the carb, it would run for a second or two, so it was definately the new pump had stopped pumping. I took it out, and checked it, but it was fine. So I had to search for an electrical failure.

Tracing the wire all the way from the pump to under the dash, I found a little black box, that had a small relay in it, on a surprizingly complex circuit board. Checking the manual, this is called the Fuel pump control unit.

It smelled of overheated elektronics, and sure enough, there was a burnt transistor on it. I love it when I can see or smell electric problems:)

I hijacked this unit from another car, and it started running perfectly again, until 2 days ago, when the same thing happened.

So obviously, the new pump is pulling more power than this control unit can handle, so I picked up some transitors that are twice as capable, and soldered them onto this circuit board. This I did last night, and it runs fine.

Now all I need to do is wait and see how long it holds, or if something else will

 

Bottom line, my problems are possibly that my fuel pump was working erratically, and finally died, and the car won't idle without proper fuel pressure. If that makes sense to you, then perhaps people can check their pumps if they are having these problems, but beware of putting any aftermarket pump in there.

 

Also, if my control unit keeps burning out, does anyone here know why this unit is so complex? I mean, it's only a fuel pump, what does this unit do?

Was wondering if I should just replace the control unit with a regular relay, but that leaves 2 wires out of the 6 pin connector that I have no idea what are for.