Tundra won't start due to a bad oil pressure gauge?

Tundra is in the shop again, this time for a failure to start issue. The truck ran fine earlier in the day, and when I tried to start it approximately 2 hours later while I was in a parking lot, nothing. It cranked like nobodies business but would not fire. Had to call AAA (glad I have it) and have it towed to my regular shop where it sat for about 4 work days due to the shop being down one mechanic. Anyway, diagnosed today as a bad circuit board behind the speedometer, tach, oil gauge, temp gauge. Apparently, a safety feature in these things causes the ECU to NOT allow fuel flow if it can't detect oil pressure. This obviously will prevent ruining the engine due to the engine running and no oil circulating through the engine. My dash display was found to have an oil gauge that was wigging out, causing the ECU to read no oil pressure. The engine will run when started with starting fluid and a manual oil pressure gauge shows normal oil pressure. Every time the engine is turned off, the same sequence of events shows up again. A new circuit board from Toyota is $150.00 and should be delivered by Wednesday. This was a new one on me. My mechanic says he has seen this before on Toyotas but not often. He said the "save the engine" feature is more common on big trucks but some of the auto manufacturers have started using it as well. He said that when tested with a multimeter, a correctly functioning oil gauge should be under 20 ohms. Mine was showing approximately 44 ohms. It was just whacky to me that it happened so suddenly. I was thinking a fuel flow problem again or possibly an ignition system component. More to come when I get the truck back later this week. Unfortunately, I can no longer say, "It has never left me hanging."

 

Jim,
Reading your post reminds me of how much I dislike all the modern vehicles. I was able to field fix almost anything and limp home from a break down with stuff built before the mid ‘70,s. Now, if it’s broken you can’t even diagnose it, much less, fix it.
Keep us updated on your solution

 

I will try to find out what trouble shooting procedure they went through to arrive at this diagnosis. Once again, no "check engine" light appeared during or after the failed attempts to start it. The "check engine" did not come on when I had a poor fuel flow problem about a year ago, which I am guessing was water and/or dirt in the fuel, so I assumed it was another tank of bad gas or something of that nature. Maybe hooking up the OBD II provided a code for them to look for, but I thought the check engine light coincided with all codes.

 

You were right. It was a fuel problem. The fuel pump is turned off when no oil pressure is detected, hence it wanting to start using starting fluid.

 

Yes, and since they were so simple to start with, nothing mysterious ever really happened. A problem under the distributor cap or a frayed wire was immediately obvious. I had a VW bug once, it just quit, a wire fell off the distributor, put it back on, away i went, and once my Ford, 240 six lost the power steering due to a burst pressure side hose. Removed the belt to the pump and got home w/o the power steering, no problem. Now we have crazy electronic systems, not to mention, smart alternators and electrically powered steering. I sold my newest (2012) car and the only, and newest vehicle i have now is the 2001 Tundra, and it's still a bit too complicated, but I will keep it as it's been trouble free since new. I have the same issues with motorcycles as well, my newest one now is a 1993 and a bit complicated as well. Progress i suppose. cheers.

 

Report back to let us know if that was indeed the problem. That is a new one for me as well.

 

FINALLY...Got the Tundra back today. 2 weeks to the day that it was towed for the no start issue. Just part of the odyssey that has been my experience with this Tundra over the past 4 months. Hopefully, my cash outlay for this vehicle will subside for a loooong time. Over the last four months, I have had the carrier bearing (driveshaft) replaced, the passenger side rear axle bearing, and now the circuit board for the dashboard gauges, AND another fuel pump. I question the need for the carrier bearing after the rear axle bearing issue was found, but that is for another time. Each of these repairs set me back $400-$500 so I have not been singing the praises of Toyota for a while. Maybe again, soon.

Unfortunately, I wasn't able to pick brains of the mechanic or the shop owner this time when I went in to pick up the truck. They are still down one technician so they are jumping in the work bay area, and the owner of the shop was out for a personal appointment somewhere.( Boy! Has he got some nerve! Having a personal life and everything!) Anyway, some may remember a thread I participated in in which I was addressing what I thought was dirty fuel or water in the fuel. The truck would bog down and hesitate when more gas pedal was applied, especially on steep inclines. I had to let off the gas and then get back into it slowly to keep going. No check engine light for this issue so when I explained what was happening to my mechanic(s), they basically said that if it ain't throwing a code, we could be looking at anything and everything. I settled on it being a bad tank of gas from somewhere and replaced the fuel filter and ran some Red Line fuel system cleaner through it. This appeared to clear things up. I went for a month or two with no bogging or hesitation issues. Then I got another tank of gas from one of my usual stations and I experienced the bog down issue again, just one time. I thought, "son of a b*tch! How much bad gas can these clowns get a hold of?!" Then about 3 days later, the no start issue that started this thread ruined my day. It was determined to be a faulty oil pressure gauge on the dash readout circuit board and as Koditten pointed out, the fuel pump will not send fuel if no oil pressure is detected at start up. I think a lot of this trouble shooting stuff is available on line and that is how these guys know what area to start looking in. The new circuit board, which is very thin and flimsy and would actually wave in the wind like a flag if it were exposed to wind, was installed with some modifications by my shop, so I am told. I was told the entire new circuit board would address all of the dashboard readouts, including the odometer. This would be a no-no if it were to set the odometer to "0" again. I believe the new board was programmed (?) to reflect the correct mileage, but I am not sure because I couldn't pick anyone's brain about the repair, at least this time around. Anyway, everything was put back together and tucked away and the mechanic took it out for the after repair test drive. And this is when he felt and experienced the bog down and hesitation issue with the acceleration. Good. It happened at the right time to the right person as far as I am concerned. The culprit? A Toyota OEM fuel pump that had been installed by this shop 2-3 years ago when the original went bad. The 2nd fuel pump wasn't providing steady voltage to send the fuel on down the line. I was told 15 volts at times, then 30 volts, then back to 15 for no apparent reason when a load or demand was put on the pump. Since the changes in voltage were erratic, that was probably when I was experiencing the hesitation issues. It probably wasn't dirty or watery fuel at all. I didn't think fuel pump because it had already been replaced once. So, yet another OEM Toyota fuel pump was installed (this requires dropping the tank and naturally I had about 3/4 of a tank in there) and all is good to go. Again. Fingers crossed. I was charged only for the circuit board, and remove and replace (2.5 hours). An ICP is the only thing listed on the invoice. The shop is going to do battle with Toyota over the faulty fuel pump issue, hoping for some kind of compensation. I like my mechanics logic because depending on the customer, he will always recommend OEM replacement parts if they are available. He says they are definitely more expensive, but so much of the after market parts out there are crap, and he spends more time now than ever before replacing after market parts he installed once because the original replacement part failed way too soon. I have attached photos of the old circuit board that was replaced. I can't figure out heads or tails of it, but maybe some of the more experienced folks on here will recognize something.







I am guessing the black plugs are located at the bottom of the board, but that is just a guess.

 

Tundra2001, thanks for posting and for the additional details. There's alot to unpack there.

1. If I understand correctly, you were having hesitation issues and suspected fuel pump

2. Replaced the fuel pump and symptoms abated for 2-3 months

3. Hesitation conditions returned, diagnosed as voltage irregularity being delivered to the fuel pump

4. The voltage irregularity is not a malfunction of the fuel system, but rather, a faulty circuit reporting the oil pressure to the instrument cluster. It's belived if the instument cluster registers no oil pressure, the engine control moduel is instructed to deactivate the fuel pump as some type of safety protocol to prevent an engine with no oil pressure from siezing.

5. Thus a faulty instrument cluster circuit board is what caused the no start condition

Is this recap accurate?

 

Koditten, can you share your experience with no oil pressure interrupting the fuel circuit if you have a chance. I would think the oil pressure sensor would send an input to the ecm first, and then to the instrument cluster or perhaps simultaneously. I can follow where the ecm would be programed to interrupt the fuel circuit as a fail safe to protect the engine, but I'm not seeing how the instrument cluster could command an interrupt action with out the ecm's approval.

 

Here is the circuit board you are looking at. Back of guage cluster.

Also find it hard to believe the oil guage on this cluster can determine fuel pump power.

Also confused how a bad pump can cause a 30 volt reading??

 

I believe you are correct. The bad sending unit feeds the ECU and the ECU makes the decision to allow the truck to start.

As a vehicle re-builder, I know for a fact that these trucks will run with no instrument cluster in place. This tells me that the the bad cluster C. board is not preventing the ECU to allow the truck to start. It had to be something else.

As for the 30 volt reading to the F. pump, that makes no sense to me. The only thing that can cause those types of readings is a failing alternator.

 

Same. You cant alter the voltage, and if the pump was trying to short or lock up it would increase amp draw.

 

This is the part I like about these threads. Several different participants go back and forth with experiences and knowledge as the rest of us try to glean what we can from all of it. The part I don't like - my truck is the cause of this lofty discussion.

Remington 351 - The sporadic bogging and hesitation started occurring about 18 months - 2 years AFTER the original fuel pump was replaced with a fuel pump obtained from Toyota. The fuel feed issues started for me about 4 months ago. In total. Again, I never considered a fuel pump issue in part because it had already been replaced, and because I thought an electronic fuel pump is either good or it is bad. No in between. I have been schooled on that as well. As far as constant voltage to the fuel pump - I can't speak to that one. I am guessing the shop went through the normal diagnosis and troubleshooting procedures that led them to concentrate on the fuel pump issue. Is there a component inside the fuel pump itself like a voltage regulator that can lead to irregular voltage flow at the pump? There may have been normal power feed to the pump, but things went whacky once the pump was in charge of things. I don't know.

Koditten - During the initial troubleshooting process that found the bad oil pressure gauge, the sending unit for the oil pressure gauge was removed and manual, screw-in-the-hole gauge was used to determine if there was oil pressure. I am picturing this procedure, I didn't witness it. When this was done, and ether or starting fluid was used to crank the engine, the engine started and ran, and once running, ran without a hitch. So, the dashboard oil pressure gauge had been bypassed, allowing the the engine to run on its' own after the shot of starting fluid. I am guessing the oil gauge prevents start up if necessary, but not the engine from running entirely. This is what I am picking up from this thread discussion coupled with what I was told by the shop.

TX-TRD1stGen - I was told by the shop owner that 15 volts will keep the truck idling with no problem. It should be at a constant voltage reading (not sure what that is) when operating correctly. The whole 30 volts down to 15 volts came into play when the engine requested more fuel. And this condition did not occur all the time. There were many occasions when I could mash the pedal a little harder and the truck responded as it should. It was the every once in a great while thing that was annoying the heck out of me. It was only due to the stars and planets aligning themselves correctly that the symptom presented itself again while the mechanic was actually driving it.

Now driving the truck with the "new" oil pressure gauge, I have noticed that the normal position for the oil pressure needle while driving at normal speeds is just a little below the middle white mark on the dash display. Before, it was dead on the middle white mark. Also, when sitting at idle, the needle goes all the way down to the white mark for "L". It actually rests on the white mark. Before, the resting spot was just a tick above a very bottom white mark. When giving it gas to pass, the needle will venture much farther into the range above the white mark in the middle. Before, it barely crept above the middle white mark.

 

This sounds exactly like the oil pressure gauge on my truck. Perhaps it is now working properly while before it was not.