Fuel pump confusion

Do you think a shop would have any more luck then the combined knowledge base here.

Expect charge more money and keep throwing parts.

Try clearing your codes again see if it starts .

What ever code is not being displayed seems to be shutting off the fuel. Is it the ECM shutting off the injectors .

Is it the Spark being shutoff??

The engine starts and runs the code trips back to starting and shutting off.

This might be the real reason the seller parked the truck thinking it was the fuel pump??

You knew going in it was a project !!

Every step is a little closer!!

 

I like this enthusiasm! This is true. I do think this is why the owner parked it and this is the same issue. I don’t think he was trying to pull a fast one knowing there was something catastrophic going on; we’re in med school together and I know and trust this guy. He said the problem began as intermittently dying after starting, which became more frequent. He thought it was the fuel pump after researching online, but wasn’t sure. For $700, I’m still glad I got it. Plus I love working on something besides medicine for a change

 

I agree ArizonaBrian! I’ve have the new Denso pump in for a few days. The fuel pressures obtained with the gauge are from the new Denso pump.

I did not monitor the fuel trims while the fuel pressure gauge was hooked up when it was running. I wish I had! I do have fuel trim data during idle at start up and 10 minutes later however.

It could be tank vent/breathability issue. I will investigate further before buying anything else

 

Can you put an inline tester on one of the spark plug wires or on one of the spark plugs so that you can observe whether you are getting spark when it shuts off?

Did you repair the cam sensor wire/shielding that you found was frayed earlier?

 

Clogged fuel filter?

 

I put a brand new fuel line filter (and pump strainer) in. I don’t think pressure is the issue anymore now that I have a new OEM pump in. According to the FSM the fuel pressure is where it should be. But thank you for chiming in! I appreciate ALL ideas

 

Surprisingly I’ve never used an inline tester to check spark. I did pull each plug out one at a time with the spark plug attached to the boot and visually confirmed they are all sparking good when I crank it. It’s really hard to tell if the spark stops first or the truck shuts off first. It appears to happen at the same time

I have not repaired the cam sensor shielding. The shielding is intricately wrapped around the wiring (and missing where mine is frayed). I don’t think I could fully restore it without buying a new CPS. But you’re right, this could be the issue, just trying not to spend more $ until I have a better idea.

If I have time today I plan on pulling off the protective pan under the motor to get a better look at the crank position sensor wiring as well. Since this is intermittent I am really leaning towards a bad connection to a sensor that tells the ECU to keep sending spark and fuel immediately after start up.

And THANK YOU so much everyone for your guidance and ideas! I REALLY appreciate all this awesome help

 

One step at a time the more we learn the closer we get.

 

Finally got around to pulling out the crank position sensor to get a look at it (despite no codes). Wires look fine but the sensor itself and the housing it sits in is CAKED with 250k miles worth of road gunk. Cleaned it all up well (with dry towel, no liquids or chemicals). Found a helpful list of fail safes and a diagram of what controls what for ignition signals (pics below).

Also took apart mess of electrical tape someone put around the wires coming from the ignition just below the steering column (maybe when they put the alarm in?) to get a better look at the wires. Turns out most if not all the colored wire jackets were partially cut, exposing the wires which were poorly taped together in a bundle, so some of these wires were likely touching… Used electrical tape to individually wrap each one. Will update when I get a chance to try it out

 

Fixed!!!!!! It was the ECU. Plugged in the replacement ECU off eBay. Starts and runs perfect every time now! Out of all the vehicles I’ve worked on, this is the first time an ECU was the culprit. Hopefully this story helps someone dealing with a similar issue. BUT, I don’t recommend just buying an ECU until you’ve ruled out ALL the sensors and possible causes first. It is also possible there was a loose connection to the original ECU (although I doubt this since I checked EVERY freaking wire going to the ECU harnesses as best as I could first and found no loose connections).

Thank you to everyone for all your help and advice! I learned a ton about this truck in the process and don’t regret a minute of it! (except when I dropped the gas tank on my face)

 

Eureka! Pat yourself on the back for your determination and refusal to give up. Best of all, since you found the actual cause, you won't have that insecure feeling that the engine might stall unexpectedly and leave you stranded. You can now enjoy the Tacoma that you got for not too much money and the knowledge that you gained while you figured this out is also a big bonus. Congrats!

 

I knew you would get things figured out!!

The lessons learned was worth the time spent.

Going to have the ECU rebuilt as a spare ??

 

Thank you! What’s ballpark cost on that? Sounds like a good idea but also expensive!

 

been a few years !! But I sent in my core and got an exchange rebuilt one for $300.00.

98 4runner!

ECM Depot in Grand Prairie TX