Hard Start solved: injectors

[tompumped]

After eight years or longer I finally figured out what it was that was causing my hard starts after the engine was warmed up. An injector was bleeding off pressure and the fuel in the rail was boiling and causing vapor lock I believe. I found this out by accident one time when I pulled off a fuel line on the engine hot and the fuel was boiling and spitting out of the fuel rail.

I always just dealt with it because I got used to it and knew how to overcome the issue. I would hit the key to fire the engine, it would fire then stall immediately. All I had to do was floor the gas pedal for clear flood mode and it would fire the second time. Then it got worse and three times in the past year I thought I was going to have to get the car towed because of flooding. I replaced the pump and the FPR with an OEM regulator recently and still I had issues.

I found a set of brand new OEM injectors for a steal online and put them in and the fuel pressure dropped five psi after a half hour KOEO vs a minute or two. The injectors I purchased were NOS from 89 and one was seized up. It freed itself and started working after I pulled out of my driveway and hammered it.

Years back I sent the original injectors out for cleaning to southbay fuel injectors when I first started having this issue and it was still present when they came back. They came highly recommended and I didn't think they could be at fault. At that time i'd had a new pump, and regulator as well.

 

[tompumped]

Throughout the years I said it's no way possible these people are getting that type of highway mileage but they are correct. I believe injectors is an often overlooked item. Throttle response is better and it might have gained a few horses.

I've only done one test of MPG since install and I have to test again. I didn't use the same pump but I will for future reference. I don't top off I wait until it clicks off.

It is vastly different. I now believe the 30mpg claims. I remained skeptical because I never had a sho that did it, but I never owned a low mileage sho. I assumed it was my oil consumption that was affecting it. Same way people say mine runs fine on 87, yeah well you don't have oil diluting your ocatane ratio which causes pinging.

 

[kevinspann]

I had a V8 SHO that would bleed off fuel pressure and be hard to start when warm. I always hypothesized that it was an injector (or more) leaking when shut off, dropping fuel pressure and flooding the cylinder(s). It even backfired once and blew the intake apart when one of the braces wasn't in place.

FWIW even my cammed 3.2 got about 29 on the highway with the cruise set to about 70.

 

[tompumped]

I thought that was the issue as well, but with the intake off I couldn't see noticable leakage. If it bled off in a minute or two I thought for sure i'd see the fuel, but I never did. I was looking for drips but I should've probably put a paper towel under the pintles to confirm which it was.

The only reason I found out about the fuel boiling in the rail was because I had to drain the tank. Within five minutes after shutting down the engine I didn't depressurize the system. I just took off the intake crossover so I could access the spring lock fittings and when I pulled off the feed line it was spitting and I could hear it boiling. It was popping and shooting out of the fuel rail. I remember hurrying to get a rag so I didn't have to worry about a fire.

I don't know if vapor lock is possible, but the fuel was definitely boiling in the rail. I constantly get in turn the key and start the car , not letting the rail fully pressurize. I'm trying to get in the habit of waiting until the fuel pump stops priming.

 

[itwonder]

Very interesting that you've noticed so much difference (in addition to the solved leak down issue) with the new injectors.