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b2000 stalls randomly

  #1  
Old 07-26-2016, 01:22 PM
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Question b2000 stalls randomly

1986 Mazda B2000 Pickup
191 4 cylinder engine, possibly referred to as a 2.0

Ok, the issue: It runs great, until it doesn't. Then it stops getting gas and chokes and dies. When it dies, it just bogs down. It might idle just fine, but if you try to accelerate, it dies/bogs down. Our longest distance without breaking down was 80 miles. (several "test trips")

When it runs, it runs like a top, but then it just dies. It may restart, it may not. You may get 20 feet, or 1/2 a mile, before it just dies again. When we get out & look when its turning over, there's no gas going into the carb. If we disconnect the fuel filter, & re-connect it, it may run again, for a short, but then dies again. If we pour gas in the carb, it runs.

History:
This was towed behind a motor home for most of it's life, so it's 140k miles are probably more like 50k running miles.
It spent 3 years sitting in a field in the hot AZ sun. Luckily pack rats didn't eat much, just a couple spark plug wires.

What we've done: (sits down to write a book)
Removed and cleaned the gas tank manually. I'm pretty sure it's well cleaned, but wasn't dipped and boiled.
New sending unit, the old one was pretty nasty.
New gas cap
New fuel lines from the tank to the metal lines that run under the cab.
New fuel lines under the hood. (from metal tubes to fuel filter, fuel pump)
New fuel filter
New check/cut valve (couldn't find one for an 86 b2000, but the 87 rx7 one looked the same except the mounting bracket)
New fuel pump (twice)
Carb rebuilt
New rubber return lines from fuel pump to metal tubes under cab
New coil, wires, plugs, rotor, cap.

In the book it says that there should be sensors in line, but these are not there and it doesn't look like they ever were. Maybe this was just California emissions stuff?
 
  #2  
Old 07-27-2016, 10:16 AM
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Originally Posted by MBAngel View Post
When we get out & look when its turning over, there's no gas going into the carb. If we disconnect the fuel filter, & re-connect it, it may run again, for a short, but then dies again. If we pour gas in the carb, it runs.
Good work ! You've isolated this to a fuel delivery problem, can forget the other stuff. I assume this is a 5-speed B2000 which has the mechanical fuel pump (and not an automatic with an electric pump in the tank).

Two things come to mind here:
1. Fuel tank is not venting properly, can try loosening the fuel filler cap temporarily and see if this helps, or just open the cap to vent (allow air in) next time it stalls out.

2. If you disconnect the fuel filter, can you get gasoline to come out the fuel line? Caution: flammable, you might need to jack up the rear end of the truck to try this, or use one of those hand-operated vacuum pumps like MityVac Mityvac Vacuum Pump - Save on Mityvac Pumps at Harbor Freight! to pull gasoline through.

3. I've replaced the mechanical fuel pump on mine a few times (lifetime warranty) but all the issues were due to leakage, not failure to pump. Lately the replacements did not come with a new plastic spacer, so I had to re-use those, and I assume that yours has that spacer under the fuel pump where it bolts on, right?

From factory, there was a filter sock on the intake tube inside the fuel tank. I know mine was sitting in the bottom of my fuel tank, I fished it out and bought a brand-new sock. Also, I have an inspection camera and my own fuel tank (Phoenix) was pristine with no rust or debris. What part of Arizona are you ???

So I'd try possible solutions 1 - 3 listed above. There's a better knowledge base for these trucks at MazdaTrucking.com too.
 
  #3  
Old 07-27-2016, 04:43 PM
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Ok, glad to know we're not totally brain-dead. We did think this had to be a fuel delivery problem, but we've tried so many things we're feeling completely idiotic. Thank you :-)

You are correct, it is a manual transmission, with a mechanical fuel pump. Yes, we've been reusing the spacer.

1. Removing the fuel cap worked once or twice, and then didn't work. Probably sometime in there we had the carb rebuilt, changed out the check/cut valve and changed more tubing.

2. we've blown compressed air thru the lines, and it's coming thru really good. The lines don't feel plugged at all. We can get gas to come out of the line when we disconnect it from the fuel filter.

The little filter on the sending unit was horrible when we cleaned the tank. The sending unit was completely shot. The new sending unit didn't come with a filter, and we couldn't find one to fit it, so we tried re-using the old one. We ended up thinking that could be the problem, so we removed it, lol.

We're pretty sure the tank is clean, but I didn't inspect it in detail, and we didn't get it dipped. Maybe it is so dirty, it's sucking **** up.. But I gave it a good washing out, we let it dry, we banged it and scrubbed out anything we could, vaccummed it so no chucks were left, and washed it again, and let it dry before we put it back. Replacing it is about all we got left on this truck, lol.

We're in Tucson, lol

So, we tried to start it yesterday, with no luck. We played around for an hour, wiggling every wire, and touching everything under the hood. It would turn over, and try to start when we closed the choke manually, but then wouldn't stay running. We disconnected the fuel line from the carb to the fuel pump, and turned the truck over to make sure it was pumping gas out, and it was. Put the hose back on, and it started, and ran. (but we didn't test drive it, she's pulled this crap on us so many times, lol)

A couple thoughts we've had would be to add in an electric fuel pump in line, and bypass the manual fuel pump. Or, we could run a line from the tank to the fuel pump outside of the system and see if we still have problems. That would track it down to the metal lines under the truck, which look fine from outside. Air passes thru these metal lies just fine when we put the compressor on.
 
  #4  
Old 07-27-2016, 05:52 PM
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From your post it doesn't look like the fuel line itself is plugged. Can you disconnect the hose at the carb inlet and direct into a jar to establish fuel is flowing from there when cranking or when engine starts (caution: flammable) ?

These trucks are well-known for having carburetors more complex than the space shuttle; many - like me - have updated to a Weber carb a decade ago, but I don't know how that will affect your Tucson emission test.
 
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