Had a no-start prob, but this is weird....

Ok, '93 HO w/ 5sp. New: plugs, cap, rotor, wires, CPS, MAP, temp sensors.

Had an intermittent problem with a crank but no fire problem. Would start after a few turns of the Ign. key. Now today, would crank all day long, but no fire. Has spark, and fuel pressure to the rail (checked buy pulling the fuel lines and there was fuel in 'em) but not a bunch of pressure. Fuel pump relay is working fine, I can hear the fuel pump buzz when turning the key, all other relays and fuses in the block are good.

What it does now is: Won't start by just turning the key. Will start if I turn the key with the accelerator mashed to the floor. It stays running after that.

What's causing this condition? Fuel filter getting clogged? Fuel pump going bad?

Thanks in advance!
Troy

Check the TPS voltage.... to see if there might be a problem when the throttle is at idle position.
Verify the fuel rail pressure at the test port..... You can install a gauge on the test fitting to check the pressure.
Check to see if any problem codes are on the ECM. On-Off, On-Off, On-Off, On......

Charles

Charles,
I cycled the key like you instructed, but it doesn't do anything with the check engine light.

The check engine light is on, how do I check the code on my '93? Where can I get the code infomation?

Thanks!

Pushing the accellerator to the floor tricks the computer into thinking you are having a flooded start situation. I would disco the battery for 5 minutes and then hook it back up. The computer will relearn the settings. If that doesn't fix it, I would suspect a bad CPS even though you replaced it. Put your old one back in or borrow one from somebody. I've got one but I'm a little ways from you.

Yeah, I already tried disco'ing the battery and resetting the 'puter - didn't change anything.

Seems to me that if the CPS was bad, it wouldn't fire even by pressing the accelerator - no pulse to trigger the injectors.

A buddy suggested that maybe I've got one or more injectors leaking down and soaking a cylinder or two. I'm gonna fire it up, pressurize the fuel rail and see what the pressure is like at the schrader valve, then wait several hours and check the pressure again to see if it changes.

I just dunno - seems like if I had an injector or two leaking down, the thing would act like it wants to fire when the dry cylinders get spark and just sputter a bit until the wet cylinders fire. Right now, it just cranks without a hint of fire until I mash the gas pedal.

Again, anyone know where I can get a listing of the codes and how to pull the code it's got now?

Thanks!

Strange.

Something everyone seems to forget with no- start problems -'specially when it cranks and cranks and nothing is happening is the camshaft position sensor in the distributor,(another hall-effect sensor like the crank position sensor) check the wires, connections, etc from that , considering you just replaced the crank position sensor - if it is functioning intermittently, it can cause some really annoying no start problems - now ya see it now ya don't type stuff.

Art,

Yeah, I hear ya, but if I understand it correctly, if the cam position sensor is malfunctioning, there won't be spark. I have spark, all the time. The whole problem seems to be with the fuel. No rich smell when cranking it over and over as if the injectors were squirting. I don't think it's getting any fuel until I mash the gas pedal then something overrides and the injectors start working.

I've got no magic but,

I'd agree that if you have any spark it's probably at the right time and you should at least hear backfires if there's any gas. So I'd look elsewhere.

Gas is the other side of the equation. Since it starts with throttle wide open I'd eliminate fuel pump and fuel pressure, injectors also. It's worth $40 for the piece of mind purchasing a fuel pressure gauge will bring...

Ok so there's spark and gas can get in sometimes. So why not when starting with the throttle closed? "throttle" keeps comming up so maybe look there, specifically the TPS mentioned in other replies.

The factory service manual gives a diagnostic that I recall is relatively easy to follow.

Someone at was kind enough to send me a PDF that explains the Jeep Multi-port fuel injection used on the I-6. I'll be glad to send it to you if you give me an address. It describes 'open loop' and 'closed loop' engine operation and says "The ECU determines a wide open throttle condition by interperting signals from the throttle position sensor. At wide open throttle position the engine will operate in open loop" Ah-ha! With the throttle wide open you've told the ECU to operate in open loop mode. Closed loop operation uses the oxygen sensor to obtain information about the air-fuel mix and adjust fuel accordingly. Open loop does not. The engine will operate continuously in open loop mode although it won't get the best fuel economy.

So maybe something about the oxygen sensor is really fried and the ECU thinks the air/fuel at start time is way to rich and cuts back the fuel thru the injectors...? But with the throttle wide open the ECU jumps into open loop, ignores the oxygen sensor, and the injectors give gas?

I'd do the diagnostic measurements on the TPS and check all the wires down by the oxygen sensor. Maybe you'll get lucky.

Just a SWAG (scientific wild ass guess) but I hope it helps...