1uz dumping fuel from headers

[Tremor]

Hello,

I had my (kind of) first start today of my 1994 1uz I am building for a swap. Today I did my first test start, Everything wired up and was cranking correctly with the proper amount of voltage and fuel flowing from the external tank and back into with fuel pressure regulator screw popping up like it should.

The engine will run for a second or two, and then fuel will dump out of the passenger side exhaust manifold. I would say roughly an 1/8th of a cup.

For whatever reason that bank continues to spit out fuel, the driver side bank is completely fine. The passenger sides plug wires all seem to fire just fine, tested with a screwdriver and can visibly see them arcing.

just a little bit lost and have not seen anything like this before. Bad injectors? Stuck valves?

Any help would be great. I am extremely puzzled

 

[ivan129]

I think you'll find it'll be condensation, (water vapour). Due to the way the crankcase breathes & pcv plumbed, 1UZ's tend to blow more condensation out the left hand bank than right. If it were fuel, you'd most likely have a nice flame out that pipe.

 

[Tremor]

I think you'll find it'll be condensation, (water vapour). Due to the way the crankcase breathes & pcv plumbed, 1UZ's tend to blow more condensation out the left hand bank than right. If it were fuel, you'd most likely have a nice flame out that pipe.

It is 100% not condensation sadly, and did throw a fireball before I gave up yesterday, There is some sign of it definitely having some combustion on that bank (including the fact it ignited the gas Lol) so my current leading theory is that either the billet rail off an ls400 that was sitting in a local junkyard for many many had a bad pressure regulator and is over fueling (not an uncommon issue it seems) or there is an injector stuck open and failed on that bank though they behaved fine when I tested them out of the intake.

I do have a set of the other style circular rails with a different pressure regulator that I will swap in tonight and I will report back, if its still dumping I will start swapping injectors and checking for wet plugs. These are the only things I could think of other then a completely hammered valve.

 

[ivan129]

Sounds like you're on the path to a solution. If its fuel (injector) or a valve; pull the plugs. Look for the wet plug or plugs and you'll find your cylinder/s with the problem. A compression test will identify if you have a cylinder with low comp, bad valve/s, or ring seal.
I worked on a 1UZ a while back that had a stuck exhaust valve on No.7. The very back exhaust valve. It was seezed open. When I removed the head for repair, I found the head gaskets had been fitted on the wrong sides causing the rear cylinders to run hotter than normal. By having the head gaskets fitted the wrong way round, coolant flow front the rear cylinders is retricted and causes the rear cylinders and head to run hotter. Kelvin, Gloverman, does a really good video on this subject.

 

[Tremor]

Sounds like you're on the path to a solution. If its fuel (injector) or a valve; pull the plugs. Look for the wet plug or plugs and you'll find your cylinder/s with the problem. A compression test will identify if you have a cylinder with low comp, bad valve/s, or ring seal.
I worked on a 1UZ a while back that had a stuck exhaust valve on No.7. The very back exhaust valve. It was seezed open. When I removed the head for repair, I found the head gaskets had been fitted on the wrong sides causing the rear cylinders to run hotter than normal. By having the head gaskets fitted the wrong way round, coolant flow front the rear cylinders is retricted and causes the rear cylinders and head to run hotter. Kelvin, Gloverman, does a really good video on this subject.

Hey Ivan,

Thanks for your comment, I somehow lost all of my plug sockets but I will be grabbing one checking that later this afternoon. I did pull the regulator and check the actual rail itself. I tested both rails with the injectors and each one having the regulator/dampener installed but I will definitely be checking them for gas later today. Both rails, with injectors installed do not have any leaks and both cycle gas perfectly fine. There is no leak at either regulator and the screw is popping up correctly.

I did rebuild this engine and did replace the headgaskets as well as the valve stem seals and checked that each valve operated correctly up and down before installing them again, also the engine has not had a single full heat cycle (or ran for longer then 4 seconds) so I don't think heat is/could be an issue at this stage.

Personally, it definitely seems like right now all signs point to the unknown quality used injectors OR somehow the injectors are shorting somewhere. I have used a cheaper injector "cleaner" from amazon that essentially manually sends signal to the injector about pulsating as you shoot fluid through it but I have not gotten the injectors professionally cleaned/balanced/rebuilt. This seems like it likely would be the case, otherwise I am inclined to be either a ring or valve issue on the certain problem cylinder, I will check the cylinders for gas and get back to ya, I will note though there remains to be no gas in the oil and zero discernable smell/level change so usually that is promising it is not a ring issue or washing out the cylinders.

 

[Tremor]

Hey guys, just wanted to report back that it was indeed a bad injector! let the gas dry off overnight, pulled all the plugs when I let it crank and sure enough cylinder 8 was filled quarter of the way up with gas!

I let it dry out, put everything back in, turned on the fuel pump and away she runs!!!!

I did shut it down from some extremely noticeable louder squealing that started up, I assume the water pump. I will drop a garden hose in tomorrow even though I did fill the block for an official break in but I am up and running!

Now to fit it in a 1992 toyota pickup

 

[P Bateman]

I'd recommend you change the engine oil too - if the injector has been hosing fuel in, its likely a decent amount has gotten past the rings and into the sump. Petrol is not a good lubricant.