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Gasoline inside brake booster

Several months ago I replaced a brake booster and master cylinder on my 1988 Ranger PU with a rebuilt unit when the booster failed. The rebuilt unit only lasted about 100 miles and failed. I replaced it, second one failed the first time I drove the vehicle (backing out of my driveway). Replaced it, the third one failed within about 100 miles as well.

In all cases the pedal got very hard and I could hear air sucking under the dash when the brakes are applied, and the engine would run very rough as well.

I thought they were all faulty rebuilds, but now that I’ve removed the third replacement unit I found gasoline inside the booster.

I previously checked the manifold vacuum at the hose to the booster and it was within specs, altho slightly on the low side. The check valve on the brake booster is working properly (by blowing and sucking thru it).

So tell me please, how does gasoline get into the booster? I won’t replace this third one until I know.

BTW, the boosters come with a little tag that says ‘warranty void if fuel found inside’. Not sure if the previous failures had gasoline inside or not, but this one had about half a cup of raw gas come out thru the vacuum port. What can cause this?

There’s probably excess fuel in the intake manifold. Is this a CFI (one injector) truck? A leaking injector would be my guess, although I suppose a coolant temp sensor could also do this. Has the truck been running okay otherwise?

Also, the ol’ blow and suck check valve test is both gross and not all that effective-- your truck’s engine can put a lot more vacuum on it than you can. I’d just go ahead and replace it, since they’re cheap.

Although not familiar with this problem, It would seem that the booster manufacturer is aware of it or they would not have attached that little tag. This must cause a good number of failures. A quick call to your dealer should shed some light.

They know that if there is gasoline the check valve isn’t working. I think an 88 Ranger is getting kind of old but if the check valve solves the problem, you can drive it with brakes.

Check the fuel pressure regulator vacuum line for presence of gas.

Thanks for the input and ideas. Greasy Jack, yes, it’s the CFI version. I hadn’t thought of an injector, but at times when it takes extra cranking to start (when it’s warmed up) I smell gas strongly. I’ve never found a leak. But the truck starts absolutely instantly–not one full revolution of cranking when it’s stone cold. I’ve never had a vehicle start so quickly. But as I say, once warmed up it takes a bit more cranking–a bit too much IMO for a fuel injected vehicle.

This truck has some other issues, but much of it is probably not related to the gas in the booster issue so I didn’t mention it, altho I suppose whatever is causing that could be an underlying undiagnosed problem all along. I didn’t want to complicate my simple question of what might cause the fuel in the booster.

All three boosters came with new check valves, and they also have a little tag that says if the check valve is removed, the warranty is void–jee, it just plugs into the rubber grommet on the booster–can’t see where that matters much as regards a warranty.

The truck was a free project truck from a friend. It both runs very well, and yet has issues that show there is a problem, somewhere. It was a one-owner truck bought new in '88, and the previous owner had the engine rebuilt (or installed a rebuilt one)for about $3k at about 148,000 miles. The truck never ran right after that, and he says he spent another $1000 trying to have the problem (unsuccessfully) diagnosed. It was ‘surging’ at idle, enough so that it wouldn’t pass the emissions test in his city.

He parked the truck out of frustration and forgot about it for a year or so, and pack rats got under the hood and ate a bunch of wires and rubber hoses. He was so discouraged when he discovered that he just gave me the truck, and I spent a year under the hood chasing every wire and hose and replacing and repairing the damaged stuff and got it running, not so well at first but as I chased other problems the truck became a nice runner, except for the brake business and the check engine light, which comes on but doesn’t affect otherwise good running. I bought a repair manual and code reader first thing, and using that I have since replaced the idle air control valve and O2 sensor, which seemed to help the surging, most of the time. It sometimes still surges at idle, but that seems to be after a ‘run’ when you come to a stop, and it eventually smooths out; but once I removed and plugged the brake booster vacuum line and the truck idled down perfectly, leading me to believe the booster was sucking air (or the one-way valve was). And that was probably the case with that booster, since it soon failed and was audibly sucking air when the pedal was applied.

The only apparent problem now is that the ‘check engine’ light comes on every time I drive it, but only after about eight to ten miles or about ten minutes. It’s always off when I start the truck, but it always comes on after driving that bit. If I pull over and shut the truck off and restart it immediately, the light will be off and remain off for that same time or distance. The code reader shows (I think, from memory) a code 41, which with the KOEO means ‘out of range voltage at the (new) O2 sensor, always lean’. If I check it with the engine running (KOER) and the light on it says the O2 voltage is out of range but running too rich, and it does smell rich at the tailpipe (a faulty engine temp sensor has occurred to me more than once but I haven’t tested it yet).

Once it was running very rough underway and it gave a ‘faulty or no SPOUT signal’ warning during the KOER test, but I’m thinking that’s another bad wire to the ignition module or the module itself in the distributor, since once it was running crappy and I wiggled the wires to the distributor/ignition module and it ran fine and that code didn’t come back. It could be that the ignition module is defective once it warms up under the hood, but one problem at a time! No brakes due to four boosters failing is the question I’m dealing with here. Tho as I’ve said, it could all be related in some strange and convoluted manner.

Look friends, I’m a decent shade tree wrench (and even worked professionally as a mechanic several times many years ago) but I’m Old School–carbs and points and wrenching type repairs, all this electronic ignition and fancy emissions controls and fuel injection stuff is a head scratcher but I do what I can do.
This truck is admittedly a work in progress (tho I might cut my losses soon if I can’t figure this booster business out). I’m not expecting anyone to diagnose this long distance, especially considering the other issues that may or may not be related. I’m sure if I keep plugging away at the wiring and so forth I can fix all that–I’ve been driving the truck and except for brakes and the check engine light it runs well and has been reliable. But this gasoline in the booster stuff is puzzling and seemed to lean towards a mechanical problem–the only solutions my old school experience hinted at was something like a stuck or burned valve, bad head gasket or similar, or even a timing issue, where an out of time cylinder (crossed wires or something) might have been sending some sort of fuel-air impulse into the intake manifold (but the timing checks out OK). I only wanted to trouble you helpful folk to pick your brains and see what could possibly cause gasoline to defy vacuum.

I’m liking the fuel injector or fuel system ideas, it fits with the smell of gas during cranking and how rich it seems to run even when warmed up–I’ll pursue that direction and see what I find. I’m open to all further suggestions and advice as well. Thanx again for the input.

Opera House’s idea of the fuel pressure regulator problem is a good idea to pursue. If fuel is leaking through a leaky fuel pressure regulator diaphragm, it is going to drain into the intake manifold. Look at the possibility that the fuel could be going directly to the hose for the brake booster and hence being sucked into the boost by the trapped vacuum inside the booster as the engine sits. The quick cold start indicates that you are getting fresh fuel into the intake as soon as the fuel pump builds pressure.

If you do find a defective diaphragm, consider doing a oil change immediately as I suspect a lot of the fuel has been leaking into cylinders and draining by the rings into the crankcase. Smell the engine oil for the scent of raw gasoline.

Let us know the rest of this saga

The vacuum hoses may be misrouted. Here are some vacuum hose diagrams. Maybe, they can help.

Hey guys, thanx for all the help. I didn’t get back here sooner as I injured my hand and wrenching was put off for a bit. Alright, to cut to the chase, per suggestions above I planned to look at the fuel pressure regulator, but didn’t have a clue how to test it, and I don’t have the Schraeder valve adapter (yet) for my pressure/vacuum pump to even test system pressure.

More googling, and I found a simple test for the FPR–pull off the vacuum line and see if fuel comes out (I’d done that already, and none did, but it was sitting for a week or so). But the lifesaver was a second test, with the hose off simply turn the key on (but don’t start) to pressurize the system and see if any fuel come out of the little vacuum line. Fuel there equals bad diaphragm, right?

Well, none came outafter a minute or so, and I shut off the key and walked away, but left the vacuum hose off. I was reading the manual maybe five minutes later and I smelled gas strongly. Going back to the truck, I found gas coming out of the vacuum line! A lot! Instant diagnosis, a bad FPR diaphragm fersure. I never would have gotten to that point without you guys.

Man, I’m excited now, this really could be the source of many or all the odd and undiagnosed problems not only I had, but the previous owner, with the surging at idle, running too rich, etc. I was less excited when I checked the price of a new FPR, but hey, problem solved! As usual, just throw more money at it–sigh.

Now at least I’m willing to put one more booster on there–except the place I’ve gotten three so far (lifetime warranty) just told me when I returned the defective one the price has doubled and they wanted $100p plus my old one, so I got my money back and I’ll shop elsewhere. Maybe I can work a discount on the FPR and the loaded booster as a package deal, ya think? Hahahaha! Ya’ll have a beer on me! Thanx again!

Glad that you’ve getting your brakes fixed. A fuel pressure regulator (and gaskets) are expensive at $35 at Auto Zone?!! CORRECTED,14900165/shopping/partTypeResultSet.htm Click here and check it out.
And, here is the brake booster: CORRECTED,14400143/shopping/partTypeResultSet.htm $59.99 This is the brake booster without the brake master cylinder.

Thanks for replying. I had not thought about leaving the fuel pressure built up while watching the vacuum hose. I would have looked at the vac hose; saw no fuel coming out; and assumed I was barking up the wrong tree. So patience wins out. Again thanks for the feed back.

I guess I should have included some instructions. There is a lot of volume to take up before it comes out th hose. A bigger leak would have caused extreme engine problems. The engine can be run at idle with the hose off if the port is blocked off at the vacuum tree and is the usual test. Suggest you disconnect the battery to reset the computer when the FPR is replaced. I have had cases where the computer would not fully relearn after overcompensating for a bad FPR over a long time without resetting the computer.

Jee, I wasn’t sure if any of you would bother to check back, thanks for the additional thoughts and support. Hellokit, I shopped around on the net and the FPR runs anywhere from about $24 up to $240–I don’t think the cheap one is the one I need, the ones I saw were for the 2.3L not the 2.9L but I’m still shopping. The expensive one is some kind of high performance thing I don’t need either. So the average price for the 2.9 engine seems to be between about $70 and $111 for the one I need. Not a killer expense, but I’ve dumped $1000 into this ‘free’ truck so far just to get it running near properly and safely, and I’m getting raised eyebrows from the Spousal Unit at the moment. It’s cost me nearly $2 a mile in ‘parts’ for as far as I’ve driven it in the year it’s been on the road. You drive it 50 miles and something breaks that needs $100 to replace–LOL! It may have a ‘new’ rebuilt engine, but he didn’t replace anything else on it!–the booster and master cylinder, tires, shocks, brakes all around and rear wheel cylinders, power steering pump and lines, idle air control valve, O2 sensor, radiator, hoses, wires…you guys know how all that stuff adds up, at least when it all needs replacing in the first 500 miles! Hahahaha!

We do need feedback, for other readers, as well as ourselves. How else could we tell if any of the suppositions got close?
On the parts, you can call Auto Zone auto parts store and tell them that you saw the part on the Internet for X dollars. The store may match their Internet prices. …and, that new gauge you’ve been meaning to get…

Hellokit, Thanks for the updated prices in the links above. I don’t recall seeing that $44 FPR in my searching–certainly the best deal compared to the $70-110 I was seeing. As for the booster, the initial problem with the original was brake fluid inside (and maybe a small bit of gas), so I had to go for the loaded one to get the master cylinder plus the booster. I could have rebuilt the master cylinder for the cost of parts, but I figgered if I bought the loaded package and either part failed, they couldn’t blame me. And it was a bit cheaper a year ago when this saga started, $100 plus core. When I returned the current one a coupla days ago the counterman did note they had gone up about 50%, as your other link shows. The ‘new’ one is supposed to be in today. I can move forward on the FPR too at that price, thanx!

Oh, since this thread might help others too down the road, I think I should point out and clarify the underlying error in my assumptions that prompted my main question. I ‘assumed’ the gasoline was entering the booster while the thing was running, which seemed counter-intuitive and impossible since there’s engine vac sucking the other way. It never occurred to me that after you shut the engine off the booster retains vacuum, and that was when it was sucking the gas. Of course where the fuel was coming from to get sucked in was the real issue, which you guys answered. I should also point out that the last booster always sucked air audibly after shutting down, an ineffective or defective check valve, as was suggested above. After I would shut it down, there was the ‘duck call’ sound as the booster vac sucked air–or little did I know, actually sucking gas from the bad FPR. So even tho I knew the booster was losing the vacuum after shut down, I didn’t put two and two together and realize that’s when the gas was being pulled inside. Sometimes we just miss the obvious because we’re looking too hard in the wrong place, or not logically following the clues and trail of evidence.

Hey, I’m nearly 60 years old and I’ve never paid an auto mechanic to do anything in my life, always done my own repairs. I even had a service station many years ago and did the wrenching, but in all this time I’d never seen or heard of gasoline inside the booster. I guess it’s not that common a problem, or at least I’d never seen or heard about it. But that proviso on the booster warranty alerted me that it’s something that could and does happen, I just couldn’t see how. My knowledge base has been expanded, and such a ‘simple’ solution now that it’s all laid out.

And finally, while it was noted above how ‘old’ this truck is–hahahaha! I traded up from a 1986 Chevette with 125k! I own a 1973 C-30 truck with 250k, and a 1986 Dodge 3/4 ton PU with 170k too and use them, I’ve never owned a vehicle with less than 100k or newer than ten years old when I bought it, I’m just a poor bottom feeder . This 1988 Ford Ranger was like scoring a new vehicle to me–newer than anything I own that is! And even fuel injected! My first one ever! It’s a learning experience fersure.

I’m in Arizona for the last 30 years, and aside from sun damage, mechanically vehicles out here last a lot longer than in New England, where I come from. I know the Car Guys are down on the older stuff too, primarily for safety reasons (no air bags, no disk brakes etc) but out here, people are still driving 1970’s vehicles around–as daily users, not ‘restored’ classics. Even a few 60’s cars are in regular use, I see a coupla early '60s Plymouth Valiants running around!

Kudos to Researcher for pointing out something that we easily forget: that the brake booster acts as a vacuum reservoir when the engine (and thus, engine vacuum) is shut off. The brake booster’s vacuum port is, then, open, via the vacuum hose, to the intake manifold. It can, then, draw air and/or liquid (gasoline) into the brake booster chamber.

Now,maybe WIFE can drive the new truck (and, know that it’ll stop!).