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post #1 of (permalink) Old 10-23-2002, 08:21 PM Thread Starter
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HELP! Jeep still won\'t start

I posted before but have new information. First, it's an '88 GM TPI. I bought a 'noid light and the injectors are getting the signals to fire, both sides. Before, I didn't think I had spark but I had the coil wire to the to the distributor off while I was checking with the noid light and saw a few inch and a half sparks from the coil to the nearest ground. I GOT SPARK.

I wasn't sure the fuel pump was running so I connected a jumper to it and confirmed it running, also popped the cap and pushed in on the shrader valve, it squirted quite a spray out at me. I GOT FUEL.

Now since it's port injected, it's not dependant on vacuum to pull in the fuel so I'd think it would start with a large vacuum leak if I had one. As a mater of fact, when I first got the engine several years ago, I forgot to plug a hole in the plenum for a 3/8" pipe fitting. It started and ran but wouldn't idle.

In checking some wiring, I had the distributor cap off and checked for rotation. It's turning. And I've done nothing to change the timing. Just pulled the entire engine for a frame change. Besides it will run with the timing way off.

So what am I missing? Every once in a while, it will make a couple of little half -hearted coughs but other than that doesn't even seem to try to start. No bucking timing, turns over real good. I've also disconnected the cold start injector so it wouldn't flood but have tried with it connected too. I'm lost.
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post #2 of (permalink) Old 10-23-2002, 09:13 PM
 
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Re: HELP! Jeep still won\'t start

What about the crank / distributor position sensor? If they don't give a signal, it won't fire. Any plugs or sensors you had to remove to get the engine out? No rags you stuffed into the intake to keep the squirrels out? Transmission hookups or computer interfaces? Neutral safety switch hooked up and working right? Relays are all there?

None of your circuits are loosing power when it cranks?

Getting fuel, getting fire, got air......
dumb question, but it is getting fuel on the intake stroke, not the compression or exhaust stroke? Same with spark... it will do you no good to get spark on the exhaust stroke.

How about your EFI computer grounds? If it is not right, it won't do anything at the right time.

How about plugging in another GM Hei module, just for kicks?

Oh well, just some ideas.

Best regards

John
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post #3 of (permalink) Old 10-24-2002, 02:12 PM Thread Starter
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Re: HELP! Jeep still won\'t start

Thanks for the response, that's what I was looking for, somebody to just throw out ideas and maybe hit upon something I'm missing.

No to all of the comments though. It only has the one sensor for rotation, the distributor. I first thought that was the problem because forgot to disconnect it and I pulled the connector off the end of the cable. I soldered the connections back, removed the computer and rung out the wires all the way to the ends. Also checked for shorting between the wires. All that is good.

I actually had the plenum and tubes off, had it covered with a heavy plastic sheet like a tarp, used to be part of a waterbed mattress. Didn't stuff anything in the holes.

No neutral safety switch. Good power and ground to the computer. No faults. Got an Auto-Xray, shows proper readings for injector pulse width etc.

Even though it's port injected, it's not timed to the piston. It has four injectors on each side, each set on a separate fuse. It fires all four at a time.

There is no reason for me to be out of time, didn't have the cam or distributor out. Even if it were a timing issue, I'd think it would either run poorly or I'd hear a backfire through the intake or exhaust. Nothing, just a couple half-hearted coughs like it tries to start every so often. I've tried a timing light while cranking, I get flashes but not at high enough frequency to really provide enough light to see the mark. I'll try again when it's darker.

Good spark, I can consistently pull a 3/4" spark at a plug wire. Like I said with the high voltage coil wire to the distributor removed, it would build up enough charge to jump an inch and a half gap.

I've cranked the engine and placed my hand over the throttle body on the front of the plenum and also over both of the exhausts. It sucks in the plenum and blows out the exhaust.

Only thing I can think of now is the diaphragm got dry in the fuel pressure regulator and cracked. I'll pick up a fuel pressure gauge tomorrow and check for proper pressure. Fortunately, I have a spare regulator. Unfortunately, it's a PITA to change. I have to remove the plenum, a fuel rail and probably a runner for clearance.
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post #4 of (permalink) Old 10-24-2002, 04:38 PM
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Re: HELP! Jeep still won\'t start

Just to eliminate a "fuel" problem ...why not just pour a little fuel down the horn? ...or..(and I didn't see this in your post - I may have missed it) is there raw fuel on the plugs when pulled?

How long was it sitting ..and did you apply any rust inhibiting (oil or whatever)agents down the cylinders before storage?

....just my .02
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post #5 of (permalink) Old 10-24-2002, 06:54 PM Thread Starter
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Re: HELP! Jeep still won\'t start

It wasn't in storage, just disconnected for a frame change, a period of about 10 days from disconnect to first attempts to start. There is no horn to poor fuel down, it's a tuned port. I thought about squirting some fuel in the plenum but I don't know how tuned port would handle that. I know the fuel pump is running, I jumpered it. I thought a little bit ago that since I suspect the regulator, I could clamp off the return line, it's got a hose portion. If that doesn't work, I'll give it a shot of fuel in the plenum although I don't know what to expect. I'm guessing it will work the same as a carb but I'm a little concerned that all the fuel will go down just a couple of tubes and only into a couple cylinders, still in liquid form, causing some hydraulicing.

I haven't pulled a plug yet, I'll give that a try. I thought I smelled raw fuel at the exhaust but it wasn't very strong.

Thanks for the comments. If I don't find it to be the fuel pressure regulator, I'm out of ideas. All comments are welcome.

BTW - on this setup, the fuel is regulated by bleeding off excess pressure to the return line. I can't just take the regulator out like I could if it were on the feed line.
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post #6 of (permalink) Old 10-25-2002, 01:56 AM
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Re: HELP! Jeep still won\'t start

As stupid as this sounds, try running a jumper from the distibutor housing itself to a solid ground. My Blazer's HEI was giving me fits, after replacing the entire ignition with no impreovement, it turned out that it wasn't getting a good ground. A short jumper between a vacuum advance screw and the firewall solved it's problem, and gave me about 2 mpg better to boot. Same thing happened (and worked) with my CJ, just no mileage boost.
post #7 of (permalink) Old 10-25-2002, 05:10 AM
 
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Re: HELP! Jeep still won\'t start

Gosh, I'm no engine wiz [img]images/graemlins/crazy.gif[/img] and I dont want to sound like a smart alec [img]images/graemlins/blush.gif[/img], but did you connect the ground strap from the engine to the frame when you put it back in? just a thought...
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post #8 of (permalink) Old 10-25-2002, 08:57 AM Thread Starter
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Re: HELP! Jeep still won\'t start

</font><blockquote><font class="small">In reply to:</font><hr />
As stupid as this sounds, try running a jumper from the distibutor housing itself to a solid ground.

[/ QUOTE ]Nothing stupid about that. I considered doing exactly that when I thought I had a spark problem. I checked from the battery post to the ground screw on the spark module and had a reading or 0.03 ohms. I've got good spark. There is also another ground for the sensor portion of the module that come from the computer.

</font><blockquote><font class="small">In reply to:</font><hr />
Gosh, I'm no engine wiz and I dont want to sound like a smart alec , but did you connect the ground strap from the engine to the frame when you put it back in?

[/ QUOTE ]Good point, and no I didn't but in my case, that only affects the lights and I had to run a jumper to the fuel pump ground. The ground battery cable I have has two extra #10 wires connected to the lug. One of those feeds only the computer, the other also goes inside the tub and feeds the dash, heater blower, windshield wiper, etc.

I do intend to reconnect the frame ground, but I've purchased two Square D equipment grounding bar kits at the hardware store. I'm mounting one on the frame with a #4 cable going to it directly from the battery cable to block connection and the other on the inside firewall of the fiberglass body fed by with a #6 braided cable daisy chained from the bar on the frame. Every ground will be run back to one of these bars. The frame will be grounded, but nothing will depend on poor connections to the steel frame which get worse over the years from oxidation.
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post #9 of (permalink) Old 10-25-2002, 04:38 PM
 
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Re: HELP! Jeep still won\'t start

Something weird happened the other day . Helping a friend, from work who ran out of gas. Although it was throttel body injection....We put enough gas into it , poured some into the throttle body and it would fire, but not start and keep running.
What it turned out to be was the top of the air filter had to be on and tight for it to start and run...without it, it would just keep on cranking.
I never heard of it before but that was the case. Since you mentioned putting your hand over the intake to choke it, I am guessing you do not have the air filter plumbing hooked up. Maybe the Mass AirFlow sensor is not signaling the computer...Just a wild guess.
good luck
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post #10 of (permalink) Old 10-25-2002, 05:33 PM Thread Starter
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Re: HELP! Jeep still won\'t start

Thanks for the comment, but no, mine will run without the air cleaner and I didn't even use the MAF for the first 5 years. That little wire that heats up is delicate and I was afraid the rough ride of a Jeep would ruin it.

The running out of gas thing was one of the first things I thought of, as in, could I have gotten the feed and return lines reversed? I double checked and I'm sure they are right. Auto-Xray shows normal injector pulse width. I bought the fuel pressure gauge today, I'll put it on and find out if it's a fuel problem.

Had to go over and take mom to the pain clinic late morning and I wound up loosing most of the day. Can't complain, she only lives a block and a half away so anytime I needed to make a parts run or something, I walked up and used her car. She claimed I hadn't used it that much but I listened to the same 20 song cd four times around.
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