How to get an LSX started for the first time?

[Chevelle LT1]

With this being my first LSX project, and for the fact that I've already had to get the engine rebuilt after a whopping total of 20 seconds run time, I could use some help: The engine is rebuilt and installed, and I am ready to try and get it started, but I am having some problems. Every time I try and start the engine, it will fire for a second or two, and then quit. I know that there is fuel at the rail, and the engine did start briefly before I had it rebuilt, so I am completely stumped. Any thoughts as to what else/where else to look? Is a shot of starting fluid a good idea? I've hooked up a scan tool, and there are no error codes.



With the comedy of errors that has been this project, I really would like to have the payoff of a running engine (picky, I know). If there are any suggestions to help me get there, it would be HUGELY appreciated.

Thanks,

~ Jason

[68lovebuzz]

Have you checked fuel pressure? Should be 58psi... Ish

[Chevelle LT1]

I actually have not. I do not have an in-line gauge. Is there an easy way to check? Thanks.

~ Jason

[68lovebuzz]

There are gauges you can buy to put on the Schrader valve of a stock fuel rail. Also, empty the Schrader valve with your finger or tool of choice after you turn the engine off. You should have plenty of residual pressure. If it just trickles out that's a sign of a possible pressure issue and possible pump failure or prob. These are my experiences.

[Chevelle LT1]

Brian -

Thanks again for the feedback/suggestions.

Update: I picked up a fuel pressure gauge, and now have an even stranger problem: When I key the ignition ON (and not start the car), the fuel pressure will come up to right around 60psi, but then it continues to drop until it stabilizes around 10 psi (certainly explaining the startability problems I have). This has been a very repeatable result.

Does anyone have any suggestions? I am running the vaporworx setup on a Rick's fuel tank, and am not sure if I may have wired something strangely, or if there is something else out there I may have overlooked (I figure I will IM Carl C to see if he has any thoughts on this one). Any and all feedback is much appreciated.

Thanks,

~ Jason

[carbuff]

As I recall, the pump that the VaporWerx setup uses has a checkvalve, so you shouldn't lose pressure at the rail. Is it possible that an injector is stuck open?

If you actually try and start the car, do you get pressure back? Depending on your ECU, most will engage the pump for a few seconds, then turn the pump off if there is no oil pressure. If you spin the engine, what happens?

[Chevelle LT1]

Bryan - Thank you for the feedback. I had a similar idea and just pulled the fuel rail with the injectors installed - unfortunately, that does not look to be the case (no visual leaking from any of the injectors).

What is so strange about this is that the pressure drops off so quickly after peaking @ 60-ish psi, in that it drops to 10 psi within 5 seconds thereafter.

Based on your suggestion, I monitored the pressure during engine start, and it does quickly come back to 60 psi, and will stay there during the entire engine start sequence. So, at this point, I truly have no idea of what the root cause is, and am at a complete loss.

Also, since my engine is the older LQ9 style, it was my understanding that there was no oil pressure switch tie-in with the ECM, at least based on my understanding of a discussion with John @ Speartech (although I could have misunderstood that point).

Thanks again.

~ Jason

[CarlC]

Jason,

PM sent.

Have you tried to jumper the relay, effectively directly connecting the pump to the battery?

Sounds like the fuel pump may not be running when the key in in the IGN position. The fuel system can supply enough fuel volume/pressure to start and run for a few seconds with the pump off before enough pressure bleeds off and the engine dies. You can either hot-wire as mentioned above or use a test light to test that power is suppled to the pump once the engine is running and in IGN. This effectively tests to see if the relay and/or relay trigger is working.

[Chevelle LT1]

Carl -

Thank you for this response and your PM. I will definitely give the jumper idea a shot first thing tomorrow morning and see if that changes things.

Thanks again.

~ Jason

[Chevelle LT1]

Hi Carl (et al) - Tried to hard-wire the pump this morning, and found that I am now registering as zero pressure at the fuel rail. I went ahead and reconnected everything back to normal, and it is also registering 0 psi. Based on yours (or anyone else's) experience, does this sound like there may be debris lodged in the fuel rail? If so, any suggestions for how to clean it (other than disassemble the rail and blow out with compressed air)?

Thanks to all for the help.

~ Jason

[CarlC]

If the pump is running and there is no fuel pressure at the rail then either the regulator/adapter is severely dislodged or the pump is damaged. I suggest removing the fuel module and inspecting the regulator/adapter to verify fitment.

Pump damage can also result when not enough fuel is put in the tank on initial fillup. The modern fuel module needs fuel pressure to work correctly in order for the venturi pumps to function. When the fuel line to fuel rail is disconnected for system flushing there is effectively no system pressure. Having the lower reservoir submerged means that fuel is always available to the pumps. When the fuel level is below the top of the reservoir, and there is no fuel pressure, the reservoir can quickly empty during flushing. There is an equalization valve that allows fuel to flow in to the fuel module but not out (check valve) but it cannot supply enough fuel flow to supply the pump during flushing. In other words, it's good practice to have enough fuel in the tank to overflow the module on initial startup.

[Chevelle LT1]

Carl -

Thanks again for all the help (and the PM's) in diagnosing this problem. Since it has been a while since I originally filled up the tank (this was all before I blew the engine in the car), things are a bit hazy, but there realistically may not have been enough fuel in the tank initially. Looks like this may be self-inflicted; and will hopefully have a chance to drop the tank tomorrow and find out.

~ Jason

[CarlC]

Glad to help Jason.

Running the pump dry will have the same effect as no fuel on initial startup. Fuel is the coolant and lubricant for the pump. Running the pump dry is all bad.

[72BBSwinger]

Sounds like you had good pressure until the pump ran dry lol. Ive been there, we all have probably. I couldnt get my car running one time and was pulling my hair out, buddy comes over and grabs a can of lacquer thinner off my shelf and dribbles some in the carb and BAM! I had plenty of gas but what I had was S^%$! Back to your deal, yes it is bad to run a pump dry, but I highly doubt you killed it in this amount of time. You may have shortened its life some though.

[Chevelle LT1]

Just to bring some closure to this one: Put in a new fuel pump and that took care of it. I would like to thank everyone for the time and feedback, and a special thanks to Carl for the help (over the holiday weekend, to boot) in diagnosing the problem, and for suggestions in how to properly prime the pump and prevent a recurrence of the same issue.

Many thanks to this community for the support.

[minendrews68]

I'm sure everyone is also glad that you came back with the post telling you had it fixed, and what the problem was. All too many times people ask for help, and when their problem is fixed they don't bother to come back and tell everyone that the problem was fixed, and what it took to fix it. Letting everyone know helps out all who may have the same problem down the road.

carl

[CarlC]

I'm glad it worked out Jason. Gasoline is the life blood of the pump. It's the lubricant and coolant, so running them dry is a no-no.

Carl