My B-II is a 87, with a 2.9. I have been having troubles with it vapor locking on me! It seems to do it only at about 10 to 12 miles. I have to let it sit for a few minutes and vent the intake off. Then it will run pretty good. But I have to get to some place to let it sit for about a half hour before I can get it to run.
I have changed - fuel pumps, filters, fuel sencer, and relays. I did change one of the return lines and it seems to run better. Gets really bad if I use regular unleaded fuel.
Any sugestions on this would be great.
Thanks guys!!

 

I don't think its really vapor lock unless someone change the fuel line routing. What do you mean by "vent the intake off"? Have you checked the vacuum line on the fuel pressure regulator for gas, tested the fuel pressure, checked for codes?

 

What happens is. When I get into traffic or just drive for about 10 - 12 miles. It acts like it is running out of fuel. On my injector manafold there is a pressure relief valve. I have to vent off the air or gases to get fuel back into it. I changed the fuel return line the other day back to the fuel filter. That seemed to work yesterday and today. Today it had a couple of rough spots but kept running. I also changed to premeum gas too. I think that helped too. I put on about 100 miles today and didn't have to stop or pull over. I think I will change all the lines and see what happens then.
Thanks for your reply and any future help!!
The Chipster

 

That valve is for test the fuel pressure, it looks like a valve on the AC system. If your getting air there I would suspect a pump problem, check the pressure.

 

Do you know that fuel delivery is accomplished in two stages?

The LOW PRESSURE pump, supported inside the fuel tank with the fuel sending unit, provides a constant fuel supply and, in conjunction with a small (black pint-sized plastic) Fuel Reservoir found on the left frame rail right about at the transfer case, helps to keep vapor purged from the lines leading to the HIGH PRESSURE pump, which needs an vapor-free supply of fuel to function reliably.

Some references will also refer to that reservoir as a "filter", but, if it's functioning as a filter, it's probably more of a gravity-type, removing the larger, heavier foreign objects that would otherwise be sent to the High-pressure Pump. Since regular replacement isn't specified, it's assumed its limited capacity isn't expected to be exceeded within the "normal" lifespan of the vehicle under NORMAL conditions.

On the inlet side of that reservoir (back end), the lower hose comes from the in-tank Low-pressure pump, and the upper one returns the vapor (if any) to a fitting located on the top of the tank. On the outlet side (front end), the upper one goes to the high-pressure pump then on to the 20-micron filter on the way to the Intake Manifold. The lower one is the Return Line from the Pressure Regulator on the Intake Manifold.

If the Low-pressure pump was failing, or the vapor return line from the reservoir was clogged or pinched somewhere on the way back to the tank, vapor wouldn't be properly removed and/or adequate fuel pressure wouldn't be available at the inlet side of the High-pressure pump.

That's where I'd look if I were suspecting vapor problems. Using a stethoscope or an ear pressed against the tank whereever you can get it there (a tube or hose might suffuce in lieu of the stethoscope) while someone else turns on the ignition WITHOUT STARTING the engine, listen for a motor-like sound coming from inside the tank. Don't confuse it with the sound coming from the High-pressure pump, located up near the front suspension's Radius Arm Pivot Bracket on the left frame rail.

If you hear a motor sound, look for the pinched or kinked (usually brownish in color) hose. If there's NO sound coming from inside the tank, start looking for open or shorted wiring coming from the connectors just ahead of the firewall travelling down the left front fender's plastic shroud, through a hole in the left (driver-side) frame rail going back to the top of the fuel tank. The wiring that feeds the Low-pressure pump also feeds the High-pressure pump. So if one's working, the other's probably got 12 volts getting to it. But a short to ground could be intermittently killing both pumps. Shorts can occur where the left frame rail harness passes through the hole just behind the inner fender shroud.

There's also an Inertia (kill) Switch, that cuts electrical power to the fuel pumps (located on the inside of the firewall above the front passenger seat's footwell), that has two wires and a connector that could be giving you problems somewhere, too.

Sometimes that shroud gets pushed up (I'm not sure HOW) enough to get caught on TOP of that harness, where the pressure it exerts against it eventually causes the edge of the hole to cut through the flex-conduit and untimately the wires' own insulation.

Keep us posted on what you find - Okay!?

 

This is what my Bronco II is doing. What about the seal on the canister under the driver side seat. What happens if their is none? Because I was always filling it up then putting it on just to crank the truck, so I wrapped it in teflon tape and the pump pulled fuel and then 15 minutes later it started stumbling again. Can I just buy the seal and problem will be solved? HELP.

MY POST!!!
Engine hesitation and stumbling

Hello i'm new to the forum but i just purchased a 1989 Brinco II and it ran good for about two months then it started. While I was pulling a trailer out of a pit the engine started hesitating. The more gas I gave it the harder it was for the engine to stay running. Now after about 15 to 20 minutes of running it does the same thing. At first I thought it was the fuel pump but its still working along with the relay. I also put compressed air through the line and primed the canister afterwad and same thing. After about 20 minutes of running it starts hesitating and when I press the gas peddle, it stumbles really bad. HELP!!!

 

For both of you, be sure to check the fuel delivery, as has been suggested. One thing I'm surprised no one has mentioned is the TFI (ignition) module. When the TFI fails, it feels just like the engine isn't getting fuel, when it's in fact a spark delivery issue. The TFI usually has to warm up before it fails (hence, the engine will start when cold, but stall after a period of driving), then resumes normal operation after cooling off (hence, it will start back up after a rest period). On mine, when the engine stalls because of the TFI, the ECA will store continuous memory codes (see www.dalidesign.com/hbook/eectest.html for description and how to read) related to the PIP circuit and/or the SPOUT circuit.

 

Where is the TFI located and what does it look like.

 

It sounds just like what I have been going through!! LOL Sorry about your luck too! LOL
The fuel pump is a good place to start. Just buy one. $90-100. I have changed every part of my fuel system. The other day I started to change the fuel lines and it has helped a lot! I have found that after many years of use. The lines become a little clogged and it seems it don't take much. I am going to change all my lines and see if the problem goes away. Now I only have a little bit of a miss once in a while.
The cnaister you are talking about. Needs to have the O-ring in it. You might have to buy a new one. They are cheep to buy or get one from the wrecking yard. I need a new seal for my gas tank. But I have to buy the whole assembly to get one. SO I am going to make one.
To access your pump in the tank. Go the easy way! Cut a whole about six inches square in the rear floor above the unit.
The Chipster

 

TFI mounts is on the distributor. As for what it looks like, a picture/diagram can be worth a thousand words. Try looking in the vehicle repair guides at www.autozone.com (the equivalent of a Chilton's manual).

 

What size bolt do I use to uninstall/install TFI

 

The TFI (or Thick Film Integrated) Ignition Module is a grayish colored plastic module fastened with two screws to the lower portion of the back of the distributor. All you'll be able to readily see is the multiple-wire harness going to the connector sticking out on the passenger side of the dristributor. The screws will be difficult to get to. Once they're removed, the module slides downward out of the pickup module located inside the distributor.

AS I RECALL, the screws (or bolts) are a hex-head, about 9/32" or 5/16" in size. They're just long enough to reach through the module's narrower dimension and into the distributor housing a half-inch or so. However, I should let you know that my memory isn't flawless on such details these days, and during those times, I'm "wingin' it".

It's rather expensive to buy a new one so if you go wrecking yard shopping for it, and replace the suspected bad one, be sure to have some thermal grease to replace what gets lost in the process. It's usually available at most electronic supply retailers and can be wither white or clear in color. Without that grease, the module will be prone to overheating, as suggested in a previous posting. The new replacement should come with just enough that special grease to do the job. All that's needed is a thin layer and don't let it get in/on any electrical contacts.

The connector is most easily removed by PRESSING the locking clip against the side of the connector housing and pulling on the connector itself or its wires. Attempting to pry it away from the connector housing might result in a broken retaining clip. If you pull a TFI unit from a salvage yard with its harness connector still attached, you'll be able to see how that clip works and why you press it down, rather than pry it up.

02Bora1.8t (and others) - If youre having to fill that fuel reservoir cannister at ANY time, I'd say you definitely have a Low-pressure pump malfunction or vapor return line clog. That first-stage pump, inside the tank, is there to INSURE the fuel being supplied to the High-pressure (second-stage) pumpis vapor-free. If the reservoir isn't perfectly sealed, you'll have fuel leaking out of the reservior anytime the ignition switch is in the "On" position.

Any seal leaks between the fuel tank and the High-pressure pump, on the driver's-side frame rail will most certainly result in that pump getting air or vapor, increasing the risk of its failure, but after frequent and repeated aggravating fuel vapor-related engine stalling problems. That first-stage pump is mounted to the fuel sending unit and is immersed in the fuel near the bottom of the tank. So, it's nearly impossible for it to get vapor into it.

The fuel tank needs to be removed, or at least lowered pretty far down, to gain access to the pump-sender combination unit. It can be very dirty in that area of the tank, so loosen the dirt as much as possible with a brush and blow it off with compressed air prior to disconnecting anything.

Hoses going to the Sending Unit fittings can be damaged if they're not carefully handled while working in that area and lowering the tank. Disconnecting them prior to lowering the tank is possible, but can be a pain, especially if you've never worked with the retaining clips used on them. Their connection fittings use special double O-rings that can be damaged as well, if care isn't taken.

Finally, the connector sending power to the pump and signals to the fuel gauge has a water dispersing grease inside it around its contacts. Use caution to preserve as much of the grease as possible if more isn't available while avoiding getting dirt on it.

Incidently, those in-tank pumps are usually very reliable. What causes them to prematurely fail is dirt and/or corrosion. Water can get into the tank over time and needs to be dispersed (into the fuel) by using any one of the fuel "gas treatment" additives such as STP or "Heet". This should be done about every six months to a year, depending on how humid the climate is and whether the tank is kept over half-full or less than that most of the time. Water in the tank can get into the pump, rusting its iron components to where it eventually binds and fails.

Also, in a similar way some "gasahol" fuels can be destructive to these immersed-type pump motors, and should be minimally consumed.

 

New gas cap anyone?

 

I have changed TFI and have all new fuel hoses. I have good presure now, but engine still stumbles after 15 minutes.

 

Pull the codes and see if there is anything there.