tippyjeep

Just like the title says! I've swapped a SD engine into my jeep and have been having trouble keeping it going. I've read a lot of posts where the engine won't start at all, or dies right after starting, but those aren't my issues.

The other day I got the engine running and set everything. I set the timing to 6* with the ESC disconnected, fuel pressure set to 48 psi w/o vacuum and have the TPS set to 0.56 mmvolts and disconnected the battery after I made all the adjustments. The engine, when it starts runs great…idles about 850/950 rpm, throttles up great and sounds like it should. I barely open the throttle and she’s rapping 4 grand. When it runs the check engine light does not come on.

The issue that I’m having is that once I shut off the engine, even after it has idled for 30-40 minutes, it won’t start again. I can let it sit for 15-20 and sometimes it will cough, but most of the time I need to let it sit for an hour or so before it will actually start again. Also, when it is running, it smells like it is running extremely rich.

When it is running and the vacuum is connected to the fuel pressure reg, I get around 40 psi @ idle. I checked the timing again with the ESC connected and the engine warmed up and the timing is around 18*. I used a timing light with a delay control on the back and dialed it in until my mark was back at 0.

My O2, MAT, MAP, oil pressure sensors, Knock Sensor and fuel pump/relay are all new.

I checked and I do have spark when it won't start.

What puzzles me is that when it runs, it runs great. I just can't shut it off or it won't start again!

Anybody know of anything I should check? Any thoughts on why it won’t restart right away?

Thanks in advance.

skibum2100

I think your injectors are leaking. How long does the fuel rail hold pressure after you stop the engine?

Another possibility...the FPR diaphragm is leaking; pull the vacuum line from the regulator and check for gas inside.

Good luck.

tippyjeep

What do you mean by leaking? I can turn the key and the pressure guage goes up to 48 psi, but when it clicks off (not cranking/power cut to relay) it drops back quickly to about 25 psi in 5 sec.

I pulled the vacuum line off the regulator several time and have never seen or smelled gas inside the line. It's a new adjustable FPR, so I hope its not bad.

I can also start the engine with a little shot of eather. Then it runs fine until I shut it off.

How do I check if the injectors are leaking? Will ohming them out tell me? - edit...I did some searching and found out how to check them..I don't think it is the injectors since it drops so fast, and the plugs have never been "fouled" or wet.

tippyjeep

Ok....dumb question. Is there a check valve in the supply line? I'm using the same fuel pump from my old Jeep efi setup and don't recall there being an in-line check valve. When I ran the new lines I ran it directly from the pump to the engine.

skibum2100

By leaking I mean dripping fuel into the intake manifold. You could open the throttle blades and smell for gas inside the plenum...

There is no check valve in the line, but the fuel pump has a check ball in it to prevent flow back (this is the case for TPI fuel pumps, I don't know about Jeep pumps).

Do you have a fuel feed and return line? If so, pinch the return line under the hood and watch what the pressure does. Does it drop as fast? Can you restart the engine if the pressure holds longer?

The best way I found to test and see if the injectors are leaking; was to pull the fuel rail with the injectors in it, place clean paper towels under the injectors, pressurize the fuel rail, and look for leaks. I had 4 of 8 injectors leave wet spots on the paper towels, even though they all ohm tested ~16.

I hope this helps.

tippyjeep

I think you may be onto something. I got it started today using a shot of ether, ran it for a few minutes then shut it off. I watched the pressure guage and when it shut off it was at 46 lbs. 5 min later it was down to 40. After about 8 minutes it hit 38 and steadly went down. I got it going again and when I shut it off I pinched off the return line with a set of vice grips. Pretty much the same story. 10 minutes after it shut down it was around 30 psi.

I can see why the pressure drops, but why won't it start again if the pump brings it back up to 46 psi upon priming? Is it basically flooding the engine?

utilityguy2

iTrader: (1)

pressure drop like that is normal. I would say your injectors are holding ok and pressure regulator is ok. Sounds like a vapor lock somewhere. are any line close to headers. if so put cold water on them and see if it starts. is engine temp normal? did you use rubber hoses on the fuel lines? I don't think it is flooding if it starts on ether.
Check your plugs for color, if anything I bet they are white-ish not black or wet.

skibum2100

All due respect to UtilityGuy2, but yes I think it is flooding. And I recommend pulling the injectors and fuel rail as described above to eliminate the injectors as the problem. Does the oil smell like gasoline (indicating cylinder wash)?

Pull the plugs again and have a look.

I hope this helps.

85whtz28

I had this problem, mine was a small crack at the top of the fuel sending unit on the feed line. Drove me crazy trying to figure it out.