Hard starting when hot

[rkvons]

Originally Posted by RustyMutt54521

rkvons -

BTW, if fuel leaked from the injector into the cylinders, would there be some black smoke (from running too rich/flooded) when it finally started? Just curious if you noticed any.

I think I remember seeing black smoke sometimes, but not always. I think the difficulty with starting it is more of an issue where the computer gets confused seeing such a rich mixture and tries to compensate, but by then it has over compensated because the mixture has corrected itself, so it has to compensate the other way. This is why mine had difficulty starting, I think. A fuel pressure gauge at AutoZone is only 15-20 bucks. This would help alot, because maybe your fuel pump is not doing a sufficient job. Also, remove the vacuum line off of the Fuel Pressure Regulator and see if there is any gas there. Mine was leaking and I had to replace it.

[RustyMutt54521]

I finally got a pressure gauge and observed my van's behavior. There wasn't any pressure when I connected the gauge (cold, no fuel spill or pressure). Pressure was about 42 psi after being pressurized and dropped to 37 after starting and while running. These are within specs.

I warmed it up and shut it off - pressure dropped more than it should have (apparently a 5 psi drop is norm after 10 min, but mine dropped 12 psi in 5 min). 15 min later I started and observed the normal difficulty - I didn't touch the gas pedal and it took 5 retries before it stayed running, followed by an RPM surge to 2k or so.

I let it warm back up, shut it off and immediately bled the fuel pressure this time. I didn't expect this - the pressure increased from zero to 24 psi in 10 min. Why would the fuel pressure increase on its own? I bled the pressure again, and after another 5 min I started it. I admit I was genuinely surprised it started in less than a second and kept running.

I repeated the last test again, but held the pressure relief button on the pressure tester for the entire 15 min. I let the system build pressure before cranking and it started in less than a second, but ran rough for another second before smoothing out. No RPM surge. So these test confirmed a more normal start when the pressure was bled.

I repeated a few more times - one time I did not bleed the pressure (therefore expected the difficult start) and observed the pressure before, during cranking, and after attempting to start. The pressure maintained a healthy range of 42 - 36 psi throughout, even when the engine quit. To me, this indicates the pressure regulator is working fine.

Finally, I did not find any fuel at the pressure regulator vacuum hose attachment. I think I can rule out a regulator problem.

The only conclusion I can come to is the rebuilt injectors are also leaking, like my original ones. But I can't shake the notion that I should have observed some difference with the new ones compared to the old. The odds just seem too high to have identical behavior.

But what would cause the fuel pressure to build back to mid 20s after being bled off to zero? It takes only 30 seconds or so and you can see the pressure start building - maybe 5 psi after a minute. I removed the gas cap to relieve tank pressure in case it was somehow coming from there, but it still built pressure after being bled. Please note if I leave the van sit overnight the pressure does go back down to zero on its own.

Any other comments or thoughts are appreciated...

Thanks

[rkvons]

I read your post and it does seem weird that it is the same as before you changed your injectors. That kind of pressure drop for the first test seems excessive. The fact that it started easier when the pressure was released does seem to point to the injectors. I'll have to admit, though, that I have not checked how mine behaves since I changed my injectors out. For the temperature increase, maybe it is due to the cold fuel being heated up once it gets into the fuel rail. When you say you let the system build pressure before starting, how long are you talking about? It seems like as soon as I turned my key to on the needle would bang to its high point.

[RustyMutt54521]

rkvons- I let it build pressure for about 1 -2 full seconds - just enough to hear the pump stop. This was a 1-man operation for a while so I did that to be safe. Once I got help and could watch the gauge it was almost instant, like your experience.

I admit I found some rebuilt injectors on eBay ... they were really inexpensive and I probably got what I paid for in the long run. They surely looked like new, especially compared to the rusty/corroded ones that came out of mine. I had them for a few months before installing so I don't even remember who I got them from. I'll probably buy new ones from a more reputable source and give that a try unless someone offers a better suggestion.

I can't help but wonder if injectors leak more when the engine is hot than cold. Otherwise, I should be able to pressurize the fuel rail and shut things down without starting (system remains cold), then come back 20 min later and have difficulty starting. Of course, the computers would attempt a rich mixture since the engine was cold... probably too many different variables. But from a rebuild perspective, I wonder if the place I got mine from could have missed a problem if they only leaked when hot.

I reread most of these posts here and the idea you mentioned about the computers sensing fuel already in the intake and therefore attempting to lean it out goes a long way to explain the behavior. I'm still ignorant about a lot of the system, so please forgive me for asking... but is there a sensor that detects the mixture in the intake? I would have assumed the injectors injected directly into their corresponding cylinder and that paradigm would require 6 sensors if I'm thinking correctly.

[rkvons]

I think you and I are about the same with repair skills. I only know what I've experienced and what I've read. Mine looked like new when I got them. Here's another suggestion. Have your old ones cleaned and tested. I did a quick search for "Fuel Injector cleaning" and went to the first site:
http://injectorrx.com/

Complete Cleaning & Flow Testing Only $18.00 per injector (1- 2 day turn around times

I kept my old ones in case I need to repeat the process in the future.

[RustyMutt54521]

Where can I get them cleaned and tested?

[rkvons]

Check (refresh) my last posting again.

[RustyMutt54521]

Thanks! I'll post progress as it happens

[RustyMutt54521]

Problem solved. I sent my original injectors to http://www.witchhunter.com for cleaning and service and put them in yesterday - the van starts as it should now. They sent out a nice report of pre/post test results, which indicated three were leaking upon arrival. Turn around was about a week, including all shipping times to/from northwest Chicago. I would highly recommend them.

When I put them in, I noticed the fuel pressure regulator was leaking fuel out the vacuum connector, so I replaced it. I had checked it the last time I replaced the injectors and it was not leaking. Oh well..

Thanks for the help - I hope this can help someone else with similar problems.

[rkvons]

Excellent! You are the man. Changing them today would have been a freezer.