Fuel pressure test, getting desperate

I'm looking for someone who has done this. '09 Tacoma 2.7 litre motor. I want to test the fuel pressure. Where and how do I put the gauge? I don't need to know how to relieve the pressure or how to disconnect the negative battery cable. Please help, truck is running shittier by the day. TIA Cheers, Dave

 

What are the driveability issues ? Do you have any starting issues or codes?

 

For the sake of argument, let's say I am at the point of troubleshooting where I need to test my fuel pressure. The info I'm looking for is how to attach my fuel pressure testing gauge to the fuel system to test pressure at the fuel rail.

 

https://www.tacomaworld.com/threads/not-enough-fuel-help.681264/page-2#post-24029864

 

How do you discharge the pressure? Which fuse to pull?

 

Not trying to be rude but if you don't know how to disconnect the battery cable you're going to have a tough time attaching a fuel pressure gauge correctly. Do you have a buddy or anyone with more experience to lend a hand?

 

How many miles are on the spark plugs?

 

And disconnecting the negative helps relieve the fuel pressure how?

 

Did a can of seafoam in a full tank of gas and that is when I believe things started going wrong. Started with a stumble under high fuel demand on a big hill hill, once. then progressed to more often with less fuel demand. Now harder starting, especially after sitting and kind of a shit idle. MAF is clean with proper cleaner, plugs are 2000 kilometres old, new air filter. New fuel pump which it didn't need. Had a shit intermittent chip key that wasn't telling the fuel pump to run and misdiagnosed as a fuel pump. Throwing a P0171 code. Toyota won't sell me a fitting to attach my fuel pressure guage to so am fabbing a connector

 

Now I see. I said I don't need to know how to relieve the pressure, but I guess I do. Blush ;-)

 

I said I do not need to know how to remove a negative battery cable. Sorry for the misunderstanding

 

The fuel pump gets power from the C/Open relay.
I’m guessing that if you pull that relay, the pump won’t run.
Crank the truck and let it run out of gas. (In the lines)
You may get some engine codes doing this (misfire, lean, ect)
Clear them with a scanner after you get done.

 

In my experience on other cars, fuel pressure is tested by first pulling the Fuel Pump fuse (location found in owner's manual) and then running the engine (such as at idle) until it dies on it's own. That basically relieves the pressure in the lines, and empties them of fuel.

That way you can disconnect them without it putting up a fight, and preventing it from spraying gasoline in your eyes.
it still may drip a bit, so it helps to wrap the line in a rag while disconnecting it, to catch any couple of drops left there.

However, I don't know where the line connections are on the Tacoma. Eventually I will need to figure this out or maybe check the repair manual to find it, because later on I want to try a fuel injection cleaner (through the line).

Then after that you probably put the fuse back in, put key to accessory on position (engine off) after opening door, so that it primes the fuel pump.
But somebody here said relay so I'm not sure if it's fuse or relay.
Actually, one time on a long trip away with the truck parked, I may have pulled the fuel pump fuse under the hood to make it less steal-able. So it's probably that one.

I don't know if it helps to bump the ignition for a few seconds to crank the engine so fuel gets sent at operating pressure. Obviously not too long because free-spinning cranking the engine without fuel is probably just gonna start wearing the battery and burning up the starter.

at which point a gauge will probably tell you what the pressure is, and you can watch to see how quickly it bleeds down (loses pressure) to know if it holds pressure or not.

Given that the Tacoma probably only uses low pressure fuel and low pressure pump (unlike fancy new cars with high pressure direct injection)
there's probably not many parts that can fail
one big possibility being the fuel pump
because fuel pumps are usually cheap parts that fail at 100k or later

I haven't heard of it being common on the Tacoma but at the end of the day a fuel pump is a fuel pump
I'm disappointed that Toyota put the fuel filter probably in-tank integrated with the fuel pump

rather than separately replaceable during maintenance like many passenger cars have underneath the car somewhere
the idea being that filters (like oil filters) clog with shit over time and need replacing
because fuel may have dirt and ethanol

it's also often said that fuel pumps can be burned up prematurely depending on where they're located in the tank, if they are ran dry because fuel is needed to lubricate them.
For example if some cheapass always waits until their tank is on E to refill at the gas station, meaning the pump is not fully submerged in fuel to cool and lubricate it.
I try to fill up around half a tank so there is always gas
but I have seen people run to E every time, drive on fumes, etc.


another concern will probably be figuring out which adapter you need on a pressure test gauge, to properly connect to the fuel line, since every make/model vehicle is different. The adapter to check fuel pressure on a BMW probably won't work on a Toyota, obviously.

 

There’s not a dedicated Fuel Pump fuse in the Tacoma.
The C/Open relay supplies power.
The relay is supplied power from a fuse, but that fuse also powers other things.
Like the engine Immobilizer. Which likely won’t let you even turn the truck on.

But, yes. You can pull the pump fuse if there is one.
Just not on these trucks.

 

Thanks all for the replies, very helpful. Ifound a plug at the firewall end of the fuel rail on my 2.7. It says it is the same plug as an oil pan plug. I bought one for $8 and modified it and will take out the plug and replace it with my contraption to test pressure. Fingers crossed!

 

Well, I managed to get the gauge attached and I've got 10 psi with my 'new' pump. Going to have a neighbor come over to confirm my diagnosis, then put the 'old' pump back in. Hopefully that will be the end of it. Tried to get the plug at the firewall end of the fuel rail out, but with an old flat faced rubber gasket, I would have stripped out the 6mm hex plug before it let loose. seemed like a good idea. Prolly would be if the plug would have come out. More later. Looking for a couple big lads to help lift the box off,... again!

 

That is quite low.... I think the specification is like 40.8 to 41.7 psig.

I would look for a leak also...

Here:

Measure the fuel pressure.
Standard:

281 to 287 kPa (2.87 to 2.93 kgf/cm2, 40.8 to 41.7 psi)

• If the fuel pressure is greater than the standard value, replace the fuel pump.
• If the fuel pressure is less than the standard value, check the connection between the fuel hose and fuel pump.

Turn off Fuel Pump.

(p) Check that the fuel pressure does not change for 5 minutes.
Standard:

147 kPa (1.5 kgf/cm2, 21 psi)
If the result is not as specified, check the fuel pump and fuel injectors.

 

toyota wont sell U an adapter/connector because it can be really unsafe

Uv replaced many parts simply guessing

if U find out fuel pum + pressure OK ...........then what

dont know what a' shit intermittent key ' is ????

filter

maybe injectors

id bet b4 pressure

 

A 'shit intermittent chip key' will occasionally not satisfy the immobilizer and therefore the fuel pump won't run. I know it sounds far fetched, but disbelieve it at your own peril. Had a spare unused chip key and has been great since. In hindsight, I wondered why once in a while when I left the key in, it would randomly stop beeping. Never thought much of it til now. Put the old pump back in and it now runs like it did a month ago before this all started. Tomorrow I will return the 'new' pump and collect my $540. Another factor in my original misdiagnosis of a bad fuel pump was the fact that Toyota truck fuel pumps don't start until the starter is engaged. Almost everything else I've worked on has a pump that comes on with the key in the on position. You can hear it to confirm it's running. When I didn't hear the pump come on in my truck with the key on, this 'confirmed' my bad fuel pump diagnosis. Thanks for listening and for all the replies Cheers, Dave

 

Iv replaced many parts simply guessing? Don't know where you got that from.