GRohr

Alright guys,

So I have been working the last 3 or 4 months building a new stroker engine to replace my 240K engine with a dying head (valve blow-by is a B). I have finally dropped in my new stroker a week ago. I am using ford 24# injectors and Champion RC9YC4 spark plugs and have beefed up my cooling system but other than that I am running everything else stock in my 87 renix system with the AW4.

After fixing an oil leak and a no spark issue, I ran the engine at 2200 RPMs breaking in my new camshaft and after about 3 minutes the engine died. I figured it was something with the air, fuel or spark so I pulled the spark plugs and they are black, black, black, BLACK.

So I am trying to decide how to proceed in fixing my issue so I can finish breaking in my camshaft. I left the gaping alone with the spark plugs which looks like 0.042 and stock fuel pressure. I have also not messed with the MAP signal at all.

So I am looking at gaping my spark plugs differently, using hotter spark plugs, changing the fuel pressure with an adjustable fuel pressure regulator. I will install an Air/fuel ratio gauge so I can try to tune the air/fuel ratio. If I really need to, I can look into different injectors.

This is my first time upgrading/modifying an engine like this so any advice you guys can give me in what to look into/try first to fix this would be greatly appreciated!

Thanks guys!

cruiser54

Stock gap of .035.

Check this:

cruiser54

Are all the ground wires at the engine dipstick tube clean and tight to bare metal?

GRohr

[QUOTE=cruiser54;3011204]Stock gap of .035.

Wow, I need a new gapping tool then haha. I checked the hose and the MAP when I first got the Cherokee but that has been 2 years ago now so that would be a good idea to check once it stops snowing here.

I cleaned all the grounds and added another ground to the block and another to the head when I put in the new engine.

I am going to clean all of the spark plugs and put them back in, do you think changing the gap of the spark plugs would help? The main reason I am not sure on the best way to proceed is I still need to break in my camshaft and don't want it constantly dying each time I get it going till I get the new system sorted out.

torque062

You can try burning that soot off the spark plugs with a torch for now. I'd say your best best is to get an a/f gauge and adjustable fuel pressure regulator and adjustable map to best tune it during your break in. Sounds like it's incredibly rich and fouling plugs.

GRohr

Is hesco the only company that makes a tunable pressure regulator for 87-90 cherokees or is there someone else. I was looking into getting one of the Air-Fuel ratio sets from Innovate DB-Series. Does anyone have a favorite AFR gauge that they would recommend?

GRohr

So I called Hesco to ask them about their adjustable fuel pressure regulator and if they thought that it would help my situation. They said that it wont stop the computer from putting in too much gas and that adjusting the MAP wasn't the best idea without also adjusting the timing.

First thing I am going to do is make sure that the vacuum line to the MAP isn't damaged and install a AFR gauge and then try it again and see how the AFR looks. Then if it is still running way too rich I will look into putting in 21 lb injectors like the people at Hesco suggested I do.

My only question is if leaving the stock gap on the spark plugs is a good idea or if I should adjust it some?

CobraMarty

Things that will make your engine run rich-
-cold start enrichment, 3 minutes will not warm the engine up
-staying in 'open loop' on cold startup
-bigger injectors
-not having vacuum hose on FPR to decrease FP at high vacuum conditions
-wide gap'ed spark plugs and incomplete burn
-MAP sensor vacuum line leak
-cold temperature

Get new spark plugs and gap to 0.035"
Put your stock injectors back in
check your vacuum lines to MAP and FPR

GRohr

Using my stock fuel injectors is a good idea, even if it is running lean I should be able to break in my camshaft and then play with what fuel injector I will want to actually use after I don't have to worry about my camshaft. I will also check the vacuum line on the FPR. Thanks

cruiser54

www.strokedjeep.com

torque062

That site should have been mentioned earlier.. the guys over there have helped me with my stroker build as well. There is a lot of good jeep engine info in the stickys too.

GRohr

Okay, i was finally able to work on the jeep today. I checked the vacuum line to the FPR and it is good. I had some leftover vacuum line from replacing other lines so I replaced the line to the MAP to make sure I didn't have a crack anywhere. I cleaned up the spark plugs and reused them. I installed my old fuel injectors instead of using the Ford 24# ones. I wasn't able to install a A/F ratio gauge yet as it hasn't arrived but I hope it does tomorrow.

I ran it for about 8-10 minutes and the hose from the water pump to the radiator got crazy pressurized and started to leak. So I turned it off and all the lines were warm but the one from the radiator to the thermostat. I took out the thermostat and tested it on the stove and it was bad. I put my old one bad in that opens at 185 F and it fixed that issue.

I ran it for another 10 minutes to finish breaking in the camshaft and the last minute or so it started running really rough. I let it idle after that and not all of the cylinders were firing.

I am not sure what the A/F ratio is but here are what the spark plugs look like.






Let me know any of your thoughts or ideas. I am happy that I broke in the camshaft and don't have to worry about it as much anymore.

cruiser54

They're dark, but not gas fouled.

GRohr

How do you tell if it is from oil or antifreeze? I put on a new head gasket and torqued the head bolts to the spec in the book but I could have messed something up with my luck haha. I will get a kit to test if there are any combustion gas in the antifreeze.

cruiser54

Looks like a little rich to me. That's all.