ThirstyGuy

A 1993 Jeep Laredo 4.0. I turn the key to on, wait several minutes, then the relay buzzes for 15 seconds or so. Then it starts right up...... But, until the relay buzzes, it'll just crank all day. I took the relay cover off(new one) hold the tips together and I can hear a slight hiss(leak) by the fuel rail.

Please help!

Thanks!

98XJDriver

To do this right you will need a fuel pressure gauge. You can get one on loan from your local car parts store, like Advance Auto Parts, or buy one from Harbor Freight. Attach it to the Schrader valve on the front of the fuel rail. Have someone turn the key on without starting the engine. Fuel pressure should go to 28 -30 lbs and stay there. If it doesn't stay there, and from what you describe, you probably have a leak in one of the injectors. Get a set of O-rings and install them in the injectors where they seat in the head. That should fix it. If it does not, the problem may also be a failing fuel pump. O rings are way cheaper and the first place to start. If it goes to 28-30 lbs and stays there, then your fuel rail and fuel pump are OK.

ThirstyGuy

Now it won't start at all...just cranks.

98XJDriver

OK, so you need to do the basics. First see if you have fuel, spark and air. The fuel is the obvious first choice. Get a gas pressure gauge and see if you have fuel pressure at the rail as stated above. No pressure? Go back wards in the system and first replace the fuel filter. Still no pressure? Then you are in for a fuel pump replacement. Do a search on this site and I'm sure you will find a "how to...".

Got fuel pressure? Then check for spark.

1. Pull a plug wire off a spark plug, put a screwdriver in the end of the wire and put the steel shaft of the screwdriver close to a metal part of the engine that will act as a ground. See if there is a spark that jumps from the shaft to the metal when the engine is cranked. If there is spark no spark....

2. ...when was the last time the truck had a complete tune-up? (Plugs, plug wires, distributor cap, distributor rotor, fuel filter and air filter.) If you do not know when it last had a tune up, I would do this first. Clean your injectors before you replace the plugs. You can do the everything except the plugs to see if that will get it started. Once it starts, get a can of Seafoam from your car parts store and follow the instructions on the can. I take a third of the can and put it directly into the intake by using the vacuum hose off the brake booster. You need to have the truck running to do this. Pull the vacuum line off the booster (on the engine firewall in front of the driver). Get a small funnel and let a little at a time get sucked in by the vacuum while the engine is idling. Put it in until the engine almost stalls, then back off a moment then put more in. The tail pipe will smoke. A lot. Put the rest of the can of Seafoam in a full tank of gas and run that whole tank through before you fill up again. Then put in the new plugs.

If you have had a fairly recent tune up and still no spark...

3. ...then it may be the CPS (crankshaft position sensor). Not a fun job to replace it, and not a cheap part, but it may well be that. Again, do a search and you will find a "how to".

Hope that helps.

jimlask

you can also check to see if its Fuel or Spark by spraying WD40 or Carb Cleaner into the Air Intake Manifold into the Trottle Body.

If the car fires right up, then shuts off after the Carb or wd40 is burned up, its a fuel problem. If the jeep doesnt start up with either sprayed into the Throttle Body is a Spark issue.

an easyer method then the other.

There is lots of stuff you can check if you find out its fuel.

and there is lots of stuff u can check if you find out its spark.

let us know.

ThirstyGuy

Thanks for all the info!!!!! Today it WILL be running!!!!

jeepfreak82

Just for what it is worth... I posted a similar question about a year ago, only, mine does start and run... Just turns over several times before it does start... I put a check valve in the fuel line, along with a full tune-up and cps and it still seems to do the exact same thing. It will occasionally start more easily if I have not had it parked for too long, that is the reason that I tried the check valve. It does build fuel pressure and runs great after it does start so I am kinda stuck there also. Anybody have any other ideas?

rexy44

There is a possibility of a failed coil pickup sensor. And check for bare wires on the lead to the distributor.