PinkFlydxx

Sorry about the length of this, but I wanted to explain the history of what has been found, attempted resolutions, and results. I sincerely appreciate your suggestions on additional items to check. I work on this as time is available and I am a year into it.

I have a fuel related problem with my

1991 Toyota Pickup
3.0 VZE 6 cyl engine (appr70k mi)
Automatic Transmission
Rear wheel drive (dually)
Toyota sold this vehicle as a cab and chassis, which Winnebago used for a Warrior RV / motorhome.



The engine never idled or ran rough prior to this problem occurring. When it ran, it seemed to run normal - until this matter arose, then died for not obvious reasons. The problem presented itself when as it was being driven It stalled for just a moment, then a few seconds later it completely died and would not restart for some time. We attempted a few things (among the list of items below), but nothing worked. After about 30 minutes (and several cranks), it finally started and I was able to make it to home about a mile away.

The next morning, I wanted to see if I could repeat the problem. It started with a little more cranking than norma, I made it to the end of our street (about ¼ mile) and it died again with same symptoms. After about an hour of letting it sit, it finally started again and I got back home. When I parked it at my home, it would not restart. I pulled the spark plug wires from cylinder 2, and one other, and found good spark to both. The exhaust had a smell of gas. I also that the oil had a strong smell of gas on the stick, and when draining it, found 2 or 3 quarts of gasoline mixed in the oil.

I directed my attention to the fuel system and components. Obviously something was allowing too much fuel into the system allowing it to flood the engine and reach the oil pan. I checked various items and components with the limited tools I had, and used some diagnostic shortcuts (found on here). But I did not find anything that was the obvious cause (fuel pressure regulator, fuel pump kicking on properly, etc). I decided to go ahead and replace the injectors as they probably had never been replaced, and it seemed to be the logical suspect of allowing too much fuel into the engine.

To reach the injectors, the plenum had to be removed (a time consuming job that makes me question Toyota’s engineering using this design and the endless hoses). Since the vehicle was several years old, the plenum removal allowed me access to items that probably had never been replaced, so I went ahead and changed the following items:

Fuel injectors (all six from Precision Injectors)
Plenum gasket
PCV valve and gasket
Spark plugs and wires
Fuel Pressure Pulsation Damper (BTW: I recommend to get OEM on this as the after market items are notorious for not having the ability torque up enough without breaking)

I also checked the function of the cold start injector and found that when the key was on and cranking, this injector opened up allow gas to flow out for a few seconds, then closing and stopping the flow.

After installing, it cranked right up after a few seconds and the engine idled/revved up/ran perfect with no indications of problems. I put a fuel pressure gage on the rail, drove the vehicle for a couple of miles, and found that it stayed around 40 psi. I allowed the engine to run at idle for about an hour to test it. Everything looked good, but then…

On Monday, I drove it to my work where I store it (about 20 miles) and about 1 mile from my house it stalled out for just a moment. It did not die and picked back, and from there it ran fine all the remaining 19 miles to my work. The following Friday, we were planning on using it for a short camping trip but I was very apprehensive about it, and decided to start it and allow it to idle for several minutes before leaving. After about 15 minutes, the engine died while idling. After trying to start it a few times, the engine made a “thud” sound and would not crank at all. This led me to believe that the starter had now failed. The oil again had a strong smell of gas which told me that our prior efforts may have been in vain,

I then started investigating further about this and found that excessive fuel flooding can lead to a hydrolock condition. Based on how the starter seem to “lock up”, I believed that this may have occurred but unsure what caused it since the injectors were essentially new. I removed the plugs and while someone watched, and the engine cranked over spraying fuel out of the cylinders. I think I was fortunate that the engine does not appear to be damaged since the hydrolock occurred during the starter cranking and did not put the same strain on the engine had it been traveling down the road. I cranked it over briefly a few times, and it turned over fine without any noticeable noises that would lead me to believe rod damage, etc.

I put the fuel pressure gage on the rail again. Without cranking using the key on, opening VAFM vane by hand, the pressure would reach the 40 psi, but within a few seconds, fall off to about 20 psi. I also removed the entire air intake box and found quite a bit of fuel in the bottom of the box.

NOTE: Before this multimeter and found that all readings across all the VAFM points were in spec, the fuel pump relay clicked, and the pump was buzzing. I then directed my efforts towards the fuel pump thinking that the pump was possibly failing causing spikes and drops in fuel pressure. Due to the location, I cut a hole in the floor under the dinette seat and was easily able to access the tank’s pump location and replaced the pump (OEM Denso) , filter bag, and went ahead and replaced the Fuel Pressure Regulator (fyi: found both pump and regulator on sale < $35 ea). Using the VAFM vane hack, found the fuel pressure initially reach normal pressure, then again fell quickly to appr. 20 psi – another gut punch.

So, if you are still with me, much thanks for hanging in. I know throwing parts (and money) at this is not the best solution, but I tried to only replace items that seemed to be the reasonable suspects contributing to the problem, or those that were still on the vehicle for over 30 years old and probably due for replacement.

I also believe that at the fuel injector, or CSI, key is on and the VAFM vane is open – based upon the pressure rising then falling quickly to 20psi with no fuel leaks found anywhere else (that I know could cause the pressure to fall).

With no other leaks found, the only means I know that gasoline can enter cylinders is through the injectors or the CSI in an open position. Therefore, my newest areas of concern are the following:

- Short in the injector wiring harness wires / circuit
- Cold start injector remaining open (possibly intermittent since tested ok before)
- ECU / ECM failure leaving the injector circuit open (unsure if possibly intermittent for this type of component)

The fact that there was gasoline found in the air intake box area would seem to favor the CSI open circuit, but I am not sure that the CSI being open 100% of the e could dump as much fuel as I am finding it the oil, etc. in such a short time.



-Could the pistons be throwing the excess fuel from the cylinders back through the intake plenum and then flowing down into the air intake box area?

-If the injectors are open at all times, how could the fuel initially reach pressure, then fall off?

-Is there something in the system that must allow the fuel to reach a pressure range at start up , then instructs the injectors to open (the ECM or some other component?).

-If so, then could that component be bad (i.e. receiving or sending incorrect information?).



I am not 100% of the order of the protocol the vehicle follows to start from being off to the other systems being aware of the engine running and providing operation adjustments or informationl.



Therefore, at this point, my next actions will are as follows:

- rebuild / replace the section of the wiring harness associated with the fuel injector
- ECU / ECM – I am hoping that this is not the cause. Despite using a similar part number for this device across other models, the one used for the motorhomes/RVs is generally believed to possibly unique operational characteristics on ECM apparently because is left Toyota as a Cab and Chassis, Automatic Transmission, and a 2x4 DRW drive. In other words, you can’t just grab one with the same major part number and have it work due to the secondary part number.

I am seeking any additional advice and expertise that you may be able to provide me regarding this situation. Is there anything that I should check, test, or diagnose that may be the source of the problem. I have literally wracked my brain about it, and nothing seems to be the proper solution.. Thank you in advance of any help.

osv

what a bizzare problem, and really not good for the truck, i wouldn't drive it or run it with that much gas in the oil.

on my 22re the fuel pressure varies with vacuum, aka load on the engine etc., not sure what it looks like after extended idling because i don't idle engines, it destroys the catalytic converter... but yours is probably gone anyway from that fuel issue.

with fuel in the intake i'd be inclined to plug the fuel line to the csi, just eliminate it as a potential problem and see what happens... can't say how fuel would get into the air box on your 3.0, i've never worked on one.

RubyCollins

Any update?

PinkFlydxx

Yes and no. Today I tried some additional diagnosis on the cause. Since this situation began, I have found fuel in the oil pan, fuel in the air box, and fuel hydrolocking the engine during starter cranks. As I do not know of any other source for fuel to these areas, I continue to keep my focus on the fuel injectors and/or the cold start injector (CSI). I have checked the CSI several times and each time it operated properly - and as such, give it a much lower probability as the source for the excessive fuel.

Today, my friend and I ran a few more checks on the engine and using a homemade noid light (a 194 light bulb with some gator clips leads). The #2 cylinder injector plug was the only readily accessible one, so I disconnected it from the injector, used a couple of pins to make extended and accessible contacts points for each of the two wire terminals within the injector plug going towards the harness. I attached the two gator clip to the two pins extending out from the #2 cylinder injector plug to the noid light, cranked the engine, and watch the light. i cranked the engine in a few short cycles and the light came on and flickered, but I think the flicker was caused by the engine's variations in speed from the cranking, but the light was on. When the cranking ended and the key still in the on position, the noid light remained on. I believe this identifies an electrical cause to the open injectors as the source. But what electrical source.
My suspects of the cause of the problem is now:
1. ECU is malfunctioning (i.e. injector driver) or
2. Injector wiring has a ground to short
If anyone has any other information that may cause the injectors to stay open, please advise.

After some additional research this afternoon, the cause of the noid staying lit (injector staying open dumping fuel) can be further identified by:a fairly simple method. With the ECU installed, if the noid remains on (no flicker/pulse) when cranking the engine and key in on position, remove the ECU and repeat cranking..
a. If the light stays on when cranking with the ECU removed - most likely a short to ground in the injector wiring circuit.
b. If the light goes off, most likely problem is with the ECU.
This seems like a logical means to isolate the cause of the open injectors.

I'm going to repeat the noid test Monday, both with and without ECU installed to hopefully reduce the possible causes by one more.