Intermittent no start - suspect transient fuel pump issue, either control issue or pump itself

My Tundra has 159K miles and never a problem till last week. However in past week, on 3 occasions the truck cranked but failed to start. In all 3 occasions truck it initially appeared to start but no response to further cracking; acted as if the initial start was due to pressurized fuel rail and transient non-operating fuel pump.

In two of these occasions I squirted starting fluid into the air-cleaner and as expected, engine ran rough for a few seconds, then surprisingly abruptly the fuel pump evidently started running to pressurize the fuel rail. In each case, the engine started then operated ran fine for several days, including numerous restarts, many restarts done hoping to trigger the problem so I could better troubleshoot the circuits to find and fix the root cause in the problem. I should note that, as yet, the engine has never stopped while driving; only failure to start on these 3 occasions.

I suspect this is a transient & intermittent problem in the fuel circuit; could be the pump itself (failing brushes?) or a transient issue in the pump control circuits. I have determined which relay directly feeds 12 volts to the pump; so if problem reoccurs, I plan to jump 12 volts to pump's + pin to better troubleshoot the problem.

Questions: Anyone have a wiring schematic for relay/fuse box under the hood?

Anyone had similar problem? and the solution?​

 

Does it only do it when engine is cold or sitting for long periods of time.

 

First THANKS for offering to help!

Answering your question, on the 3 occasions to date, the engine was warm when the issue occurred, though last had been off for about an hour. Sounds like you may be thinking fuel rail may have lost full pressure; The truck has seems to always stated on first cylinder and I typically rotate the key fast, thus fuel rail appears always full. Additionally on two of the occasions the engine did fire on first several seconds, then stopped firing, suggesting loss of fuel pressure in fuel rail; In two of the occasions a good shot of starting fluid in the air cleaner fired a but rough, then fuel rail abruptly filled and engine operated fine for several days....

 

Welcome!

I am no expert,however i believe in taking simple steps first.

Have you tried swapping the fuel pump relay with another like unit,and seeing if anything changes?

I once had a Honda Accord that exhibited similar symptoms. I even went as far as to drop the fuel tank and put a new pump in.

Several days later it did the same thing. I was frustrated. It ended up being a bad fuel pump relay. Something internal with the solder joints made it have an intermittent problem.

Perhaps someone else can chime in who has experienced the same thing with a Tundra.

I do recall reading somewhere that the Flex Fuel Tundras can have an issue similar to your description. I do not remember the bulletin fix on that at this moment.

 

Great suggestion; simple to try. However I probably have successfully started truck 50 of so times since the last "no start" so chasing a transient/intermittent problem is tough to find, especially to know for certain that it is truly fixed.

I spent 50 years working at NASA in Houston, much of it doing failure analysis on mechanical and electrical failures that occurred during ground testing and many that occurred in space flight. A main guiding rule was to be extremely cautious to ascertain that we really found the true root cause of the failure, as opposed to "hey that explains it". Currently I am hesitant to drive it on a trip until I know it is truly fixed.

 

Do you have an aftermarket remote start or alarm with a bypass module? I was having intermittent start problems with my 15 SR5, turned out the bypass module was faulty.

 

Ok when it was cranking did it crank slow or was it a strong crank. And flex fuel trucks are tricky. Sometimes the truck thinks its running on e85 but its really not.. If its only on start up check your thef system and check your fuel rail pressure. Only thing i can think of is when the engine is hot the engine will crank slower when hot because the advanced timing putting more strain on the engine therefore cranking slower. Try to put 93 in it. For me it starts better with 93.

 

If the fuel pump was having intermittent issues or failure ... why would squirting starting fluid solve the problem? Where did you spray and is it possible the fluid cleaned up the MAF sensor somewhat? Something to check and also check the intake area.

Someone suggested changing the relay ... Since you don't like to shoot from the hip, how about testing the relay first? It should be an easy test.

Less likely scenario:
New fuel filter resolved a few issues with one of my old cars. Your car doesn't have the same symptoms but is the filter easy to access and replace. I would do this before touching the fuel pump assuming it's easy to replace. It won't be a perfect root cause analysis ...

last but not least and if I had to guess ... is it possible that you had some bad or dirty fuel which caused intermittent issues and later cleared? maybe a little water in the fuel?

You can then dive in deeper as needed.

 

I will try to comment on the many thoughtful suggestions.....in order received ...and thanks to all for helping....

No aftermarket starter nor alarm

Cranking speed is always Fast and engine always starts very quickly,; been that way since new. Also is not flex fuel.

TTund16 comments: regarding intermittent fuel pump failure; one thought is brushes could be worn to point that contact with commutator is marginal; if a brush has insufficient contact to start pump but spraying in starting fluid caused sufficient "rough" operation that jiggles enough to again make sufficient brush contact to operate pump and pressurize the fuel rails. Admittedly not a crisp story but may bave some merit. The fluid was sprayed onto the air filter. Incidentally the main intent of spraying starter fluid was to verify that the ignition system was operational, thus pointing to a lack of sustained fuel. In all 3 cases on interment starting, The truck always fired on initial start, pointing to thought that fuel rail was still pressurized from pervious "on" cycle that then bled off because rail was not being resupplied.
As to changing the relay, I had previously pulled it; ran ohms check on coil and powered coil to verify relay closed. Also the connector pins all looked clean, both on relay and in socket holes. As to a problem with a fuel filter, if being restricted, the pressure drop would be most noticeable when I am accelerating from "0 to 60 in 8 seconds" especially pulling my 5000 lb boat ( I tease) but the point is that the fuel flow rate during startup in an order of magnitude less that during flooring the engine. Regarding water in fuel, if water in added during refueling, obviously it is in the bottom of tank so if present gets sucked up shortly after fillup...and my 3 incidents were in half to 1/4 tank levels

Again thanks to all for trying......

Am still stumped

 

Also should mention that I have repeated starting some 100 times since the last incident and as yet no additional non-starts; trying to find an intermittent/transient problem is frustrating!!

 

I can't help with wiring diagrams for 2007, but I can tell you what I see for 2015.

Instead of applying 12V to the fuel pump, I would try wiring a temporary test light across the fuel pump to see if power is being delivered continuously with the ignition switch in "run" position. Extend test light leads into the cabin so you can observe when trying to start. If power is being applied continuously to the pump with the switch on, then the problem is mechanical. The problem is either an intermittent fault in the pump or intermittent strainer obstruction. Drop the tank, clean out the trash, and replace the pump.

If you find you're losing power at the pump intermittently, then you'll have to work backwards from the pump with the test light until you find the fault. FOLLOWING WIRE COLORS/NOMENCLATURE FOR 2015: Fuel pump wires from the fuel pump control unit (fpcu) are blue (12V+) and red (12V-). Twelve volt battery power is supplied to the fpcu through the fuel pump relay with a white wire to fpcu connector, then black with white stripe, and then black wire into the fpcu. Engine Control Unit (ecu) signal to fpcu is a beige wire. If you're losing that ecu signal intermittently, then you will have to troubleshoot all the permissive inputs to the ECU that would prevent starting. The fpcu will have a ground that is a white wire with black stripe...I would check that ground before anything else.

 

Maybe this will help
https://workshop-manuals.com/toyota.../system_information/specifications/page_4550/

 

Have you changed your spark plugs?? Have you tested the battery?? near dead batteries or bad connection can cause weird behaviors on the engine. Rough idle may dictate a misfire somewhere, so you may want to inspect your spark plugs and clean your MAF. As stated above check your fuel pump relay. Also double check that you have fuel.
My 07 is empty at 1/4 tank. My fuel sender is off and it will die at a 1/4 tank remaining, so you may want to do some math and watch your gauge and figure how many gallons you're putting, for example I dump in 24gal at a 1/4 tank, so by definition its empty. Best of luck.

 

John,

Great suggestion on adding light in parallel to fuel pump; that data will definitely help in troubleshooting. However except for the 3 incidents weeks ago, no further incidents have occurred and that included some 100 starts, many trying to get have problem to reoccur so I can fully investigate so I will not worry about using the truck on a long trip out of state- as I am hesitant to be exposed to on road breakdowns, especially a long way from my shop.

A question: does anyone know if the 2007 Tundra have a pressure test port on the fuel rail circuit?
I am toying with idea of adding an emergency "Backup" fuel pump in parallel with tank pump, just in case.....to get truck safely off road in case of failure occurs while driving; the 3 incidents occurred during starting, wherein the truck fired for s second then evidently stopped because the fuel rail was not being resupplied, through minutes of cranking, and after a shot of either, the engine fired then ram fine, for 10 miles bank home. The next day while at an intermediate stop, the incident repeated, all on the same tank of fuel, and said tank was not refilled until driving some additional
and thanks for your "thinking out of the box" on the light idea......Great idea - though in some 100+ recent restarts, no additional no-start problems.

As to suggest that fuel tank fuel possibly being empty, definitely not the issue; after last incident, I drove some 150 additional miles on same tank and no additional no-starts.​

 

If you have continuous power to the fuel pump with the switch on, trouble-shooting fuel pressure would actually be a smart next step before assuming the pump is bad. A helper listening close at the tank with a stethoscope may be able to confirm if the pump is actually running during an unsuccessful start attempt. If the pump is actually running, then you may have fuel pressure regulation problems at the engine.

I have no experience trouble-shooting Tundra fuel systems, but I did some research on a fuel pressure regulator question once. (Yeah, I know. ) What I remember from that thread is that Gen2s are easier to trouble-shoot fuel pressure than Gen3s because of the fuel line connectors are less difficult and the fuel system configuration less complex. Toyota's Gen3 shop test rig has to provide for excess fuel bypass and has several fuel system connection points at the engine. Trouble-shooting Gen2 seemed to require a simple pressure test set-up borrowed from an auto parts store.

I personally wouldn't consider jerry-rigging an auxiliary fuel pump, not even as a temporary solution to this problem.

 

John,

You mentioned a fuel pressure regulator in gen2 systems; a question: is that regulator a simple "relief valve" in the fuel rail supply line that returns excess flow back to the tank, keeping the rail pressure in the 40 psi range, or is the regulator more complex, one that monitors engine speed, throttle setting, etc.

Also I assume that the pump is a single speed (basically fixed flow rate) as opposed to later models that may be 2 speed (high & low flow)?

I should also mention that despite several hundreds resent engine starts, I have yet to have a repeat of the 3 "NO-STARTS" of several weeks back. Also I implemented your suggested parallel light but as yet the engine starting has worked per design.

Finally, I thought I read somewhere that the pump "ground" wire is not a direct short back to battery ground but rather that it has a variable resistor in series with the ground that in effect modulates the voltage to the pump. Do you or anyone have any insight on this topic?

Thanks for the support.

bjr

 

Is your rig a FFV? If it is then there is one thing that seems to help them DON'T use E85. Use 87 or 92 octane. There is also 2 T-SB's that pertain to this problem.
1) Re-flashing the ECM, T-SB-0058-13, and 2) Re- flashing the ECM and deals with fuel pump, T-SB-0166-19. But...….. the best recommendation was the use of regular fuel instead of the E85. There is a most recent thread on this

https://www.tundras.com/threads/extended-crank-thoughts.66308/

This may help. I would try a tank of non E85 if you have not yet tried it?

 

Good question, but I can't definitively answer. Fuel pressure regulators have been around since fuel injection began. I suspect all are a simple pressure relief regulator with the set pressure being adequate to provide full injector flow at all operating conditions.

Yes, single speed for fuel pump would be my assumption as well. Two discrete speeds would likely require an additional wire to the fuel pump/sender assembly, but I suppose two voltages or infinitely variable power from the FPCU could be provided on a single wire.

I have no insight into variable fuel pump speed, but I can confirm that the fuel pump on Gen3 does not have a direct battery ground. On the 2015 wiring diagram, the fuel pump wires at the FPCU are labeled "FP" and "FP-". This indicates to me the fuel pump is wired in series with a voltage loop from the FPCU. The FPCU does have a ground wire that attaches to the nearest grounded structure. As far as the FPCU having a variable resister in the fuel pump wiring, I have no clue.

 

They all are very simple. Monitor operating pressure 40 ish PSI and return anything to the tank that is over the regulated system pressure to keep from blowing rubber lines, gaskets etc. And agreed that 40 ish PSI is adequate for all demand on the injection system. Most pumps are capable of putting out anywhere from 50-80 and maybe more PSI, but regulated to 40 ish PSI system pressure.

 

Did you ever figure out this issue?
I have a 08 and I have had this same issues for a few years now. Very spontaneous, no rhyme or reason. Always just let it sit for sometimes 30 mins, other times hours, and it finally would start normally and that would be it for weeks or months.
Thank you