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Fuel Vapor pouring out from back of engine (after top end rebuild)


KootenayBoy

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I recently had the heads of my Mazda B4000 (94 Ranger) now its extremely hard to start when cold you need to madly feather gas and over rev until it gets warm then it idles fine. except from behind the passanger side head a white gas vapor pours out though Im unable to see exactly where it looks like from the head or head gasket area even with mirrors or cell phone I cannot see it I can feel it see it smell it but not see.

any ideas? Ive timed it checked plug wires etc but that is for the hard start not the fuel vapor. I have pictures and video but cannot post them here

the truck is for sale and I would like to fix before loosing sales and money, any help appreciated
 


Rock Auto 5% Discount Code: 70D65189E6D8FF: January 5th, 2022

RonD

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Welcome to TRS :)

No gas pedal on fuel injected vehicles, they are "air" pedals now

So adding more air helps it start up.

On the lower intake just above thermostat housing there is a 2 wire Sensor, ECT(engine coolant temp) sensor, make sure it is plugged in.
ECT sensor tells computer to run in Choke Mode when engine is cold, all engines need to be "choked" when cold, or they won't run well until they warm up.
There is a 1 wire temp sender for the dash board temp gauge near it.

Fuel injectors have "O" rings on each end to seal them between fuel rail and intake.
Fuel injectors can usually be turned a bit after install so not a supper tight fit but snug, try turning a few injectors and see if #3 is too tight so "O" rings can't seal properly.

On the front top passenger side of the engine is the Fuel Pressure Regulator(FPR)
The FPR will have the Return fuel line connected to it AND a vacuum hose.
This vacuum hose runs to the back of the engine(passenger side) around the upper intake and is plugged into the Vacuum manifold on drivers side of upper intake rear.
If FPR diaphragm was leaking then vacuum hose would have fuel in it and that could be leaking out of the hose at rear of engine.


Coolant white vapor
At each corner of the lower intake is the crossover passages for coolant to flow from head to head on a V engine.
So any corner can leak coolant, including passenger rear corner, if gasket did not seat properly.
 
Last edited:

KootenayBoy

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Manual
Welcome to TRS :)

No gas pedal on fuel injected vehicles, they are "air" pedals now

So adding more air helps it start up.

On the lower intake just above thermostat housing there is a 2 wire Sensor, ECT(engine coolant temp) sensor, make sure it is plugged in.
ECT sensor tells computer to run in Choke Mode when engine is cold, all engines need to be "choked" when cold, or they won't run well until they warm up.
There is a 1 wire temp sender for the dash board temp gauge near it.

Fuel injectors have "O" rings on each end to seal them between fuel rail and intake.
Fuel injectors can usually be turned a bit after install so not a supper tight fit but snug, try turning a few injectors and see if #3 is too tight so "O" rings can't seal properly.

On the front top passenger side of the engine is the Fuel Pressure Regulator(FPR)
The FPR will have the Return fuel line connected to it AND a vacuum hose.
This vacuum hose runs to the back of the engine(passenger side) around the upper intake and is plugged into the Vacuum manifold on drivers side of upper intake rear.
If FPR diaphragm was leaking then vacuum hose would have fuel in it and that could be leaking out of the hose at rear of engine.


Coolant white vapor
At each corner of the lower intake is the crossover passages for coolant to flow from head to head on a V engine.
So any corner can leak coolant, including passenger rear corner, if gasket did not seat properly.
Thank you, I will check that out tomorrow in the daylight I love TRS I found it years ago and just rejoined yesterday its the single best site online for trucks even if your not a Ford owner TRS is beloved even in dodge forums lol Ill have to check those points as I did the tear down I rebuilt ported and polished the heads but was injured and hired a backyard mechanic to do the reassemble kind of regretting it now but.....

thank you again
 

KootenayBoy

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update

Ok following your advice (thank you by the way) I re did all the Vacuum lines they were all cattywampus, the mechanic Id hired to put it back together struggled with it as I did eventually I brought my laptop out stuck it on the engine and had like 15 tabs open until I figured it out.

the hard starting is seemingly cured it starts and runs with a minimal pedal feathering which makes me very happy the vapor escaping minimized a but in the beginning but as it warms up

by the end of the nights work Id discovered that the vapor escaping is coming from the crank case and its definatly gas vapor as when I took the oil filler cap off it was chugging out f there like a choo choo train.

so Im happy that I saw that as I feel Im closer to the cause and Im hoping the cause is a simple ish fix, its got to be coming from a cylinder on a up stroke because its chugging out not seeping and increases when you apply more throttle, Im totally guessing (educated guess but a guess none the less)

Ive uploaded some pics and vid of whats happening Id love some insight if anyone has some :) (other than fill it with gear oil n sell it in the rain at night lol)

https://drive.google.com/open?id=0BwQJHIjzSZa2eGhNSG02aXVZeEE

thank you in advance for reading


Welcome to TRS :)

No gas pedal on fuel injected vehicles, they are "air" pedals now

So adding more air helps it start up.

On the lower intake just above thermostat housing there is a 2 wire Sensor, ECT(engine coolant temp) sensor, make sure it is plugged in.
ECT sensor tells computer to run in Choke Mode when engine is cold, all engines need to be "choked" when cold, or they won't run well until they warm up.
There is a 1 wire temp sender for the dash board temp gauge near it.

Fuel injectors have "O" rings on each end to seal them between fuel rail and intake.
Fuel injectors can usually be turned a bit after install so not a supper tight fit but snug, try turning a few injectors and see if #3 is too tight so "O" rings can't seal properly.

On the front top passenger side of the engine is the Fuel Pressure Regulator(FPR)
The FPR will have the Return fuel line connected to it AND a vacuum hose.
This vacuum hose runs to the back of the engine(passenger side) around the upper intake and is plugged into the Vacuum manifold on drivers side of upper intake rear.
If FPR diaphragm was leaking then vacuum hose would have fuel in it and that could be leaking out of the hose at rear of engine.


Coolant white vapor
At each corner of the lower intake is the crossover passages for coolant to flow from head to head on a V engine.
So any corner can leak coolant, including passenger rear corner, if gasket did not seat properly.
 

RonD

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Recheck the coil pack spark plug wiring
3 4
2 6
1 5
Front

The 5 6 4 side often gets mixed up.
Also follow each spark plug wire to it's cylinder
Ford numbering for V6
3 6
2 5
1 4
Front

PCV Valve pulls oil vapor from the crankcase valve cover area
It creates a slight negative pressure in those areas if working correctly

So check the PCV valve and clean its hose to intake.
Also check the vent hose from oil filler tube to Air tube, it brings in fresh air but also sucks out oil vapor at idle when PCV valve is mostly closed.
 

KootenayBoy

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plug wires

Ive double checked the plug wires twice and they are in the correct order (I pulled them all and started over) there is one wire on the #5 cyl that has cracking on the exterior I cant replace atm so I taped it. its the best I could do for the moment.

the Valve yout talking of is the one on the valve cover driver side by the firewall? I was trying to re do the vacuum lines yesterday but it was an exercise in frustration but I think Ive got it at least close I did try to see if it was the problem while it was running I connected and disconnected the vacuum lines to see if it stopped the chugging of vapor.

there is also a little white froth on the filler cap but NONE on the dipstick o rad coolant so Im assuming its not a coolant to engine leak but Ive been wrong before (once or twice lol)

thank you for this Ill check it today when the rain stops


Recheck the coil pack spark plug wiring
3 4
2 6
1 5
Front

The 5 6 4 side often gets mixed up.
Also follow each spark plug wire to it's cylinder
Ford numbering for V6
3 6
2 5
1 4
Front

PCV Valve pulls oil vapor from the crankcase valve cover area
It creates a slight negative pressure in those areas if working correctly

So check the PCV valve and clean its hose to intake.
Also check the vent hose from oil filler tube to Air tube, it brings in fresh air but also sucks out oil vapor at idle when PCV valve is mostly closed.
 

KootenayBoy

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Joined
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Reaction score
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Vehicle Year
1994
Make / Model
mazda
Transmission
Manual
Camshaft synchronizer

Photographs on a google drive to show what Im seeing.

https://drive.google.com/open?id=0BwQJHIjzSZa2eGhNSG02aXVZeEE


Ive never dealt with a Camshaft Synchronizer before so its Im going in blind, that said I finally managed to get the top off (and if I ever meet the designer of this engine Im going to kick him in the nutz) mine did not have bolts holding it in, instead there were two screws in a craptastic location.

once i undid them the top fell right off and from everything Ive seen on youtube thats not to happen. does that mean its pooched?

Can the crankcase gas escape through the sensor itself or is that sealed? because this ones sensor was loose though the cap was tightly secured it was by no means sealed and inside (as seen in the pics ) the inside has some varnishing etc

Im really trying to sell this thing before the snow flies and its hard to do that when its pissing out crankcase gases..

any tips info, links greatly appreciated :icon_thumby:
 


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