plugs and gap for fuel injection

[8177]

Hey folks, been lurking but not posting. Life has once again slowed down so we can start driving the jeep. Many may recall my trials while installing a howell fuel injection kit and trying to sort throught the mess the PO left me with the wiring harness. Oh we've taken it out for little weekend adventures but nothing serious. So here we are a short while later. I've been driving the jeep as my daily driver and I'm telling you its a blast but something is amiss. My MPG has dropped and and there is the smell of fuel in the cab. No codes logged on the computer. I like to keep things simple and start with the timing and plugs. There used to be a write up somewhere on the plug part number and the gap and the timing. For some reason I sort of remembered that I either needed different plugs or needed to re-gap the ones I had but my notes were a victim of the "Big Office Purge" brought on by the wife duing this years spring cleaning. I was going to double check everything but I cant find the article. Anyone have any numbers for these things or a link to the article. I'm sure I'll be checking the MAF sensor and O2 sensor later on but I'm hoping the cheaper alternative of plugs and timing may help. I've called howell and I need a fuel pressure gage to check the pressure at the supply and return first before we can get any further. Anyway thanks in advance for any tips.
Jim

 

[jps4jeep]

I am not super familiar with the Howell system, but if it has a MAF and o2, it should be able to rear a rich condition and accomidate by leaning out fuel. How old is your fuel tank? IIRC for the howell system to work, you need to plumb a return line to the tank. I am thinking that return might be corrupt and that is causing the odor?

 

[8177]

The fuel tank is the original but there is a new sending unit installed. All the evap lines and canister are new. I put a gauge on the supply and return lines at the throttle body and they are well within Howell's specs. It never seems to come out of the fast Idle condition at start-up Howell said stock plugs and gap and 6 to 8 BTDC on timing. I have new plugs to install this weekend and a new temp sending unit. I'll check the timing then. My round trip to work is 30 miles. I was off Monday or the holiday so 3 days so far and down to below 1/4 tank. when I fill u I will calculate the mpg. Thanks for the ideas.

 

[greg92jeepxj]

Hey Jim . Read the posts and am trying to reflect on your build from back in the day. Glad to see that you and the misses are driving the jeep more now than it being on jack stands and the hood up . Took a fast look at the PDF for the Howell system I kept from then and as I thought , the system has its own ecm , since it is designed to introduce a fuel injection system to a vintage vehicle without a ecm/ECU . My first thought is the ecm is failing to step down the idle air control motor . I would think that since a coolant temp sensor is installed , the ecm would know to go to closed loop and maintain a normal curb idle. I'm sure a check engine light of sort has been installed so wondering if a code has been thrown ? Was not posted so I guess not. Strange.
I see your dilemma. My second thought is that the ecm itself may have a fault ? I know you installed it all so was wondering what your feelings are of my thoughts versus what you've already diagnosed and any conversations with Howell. But as you know , an ecm or PCM is the controller for the iac motor and I believe that is why your tank is draining your wallet.
Had an issue with a quadrajet once that to get the truck home I had to raise the fast idle just to keep it running until I can tear down the carb. Man , did it kill that tank of gas !
This problem your experiencing just sounds too much like my experience with that K5 blazer.
tell me what you think . Hope this helps . Greg
p.s. - just reread that your replacing a CTS , we'll wait to see the results , may have an effect if the current one is out to lunch/ out of spec.