KadeH

Ok to start, I've replaced cam and crank sensor, new plugs for my injector's battery and alternator. my car will start with starting fluid but doesn't get gas. my fuel rail has pressure at all times. I can't see anything major wrong with my wiring I've checked my all the harnesses in the engine bay. my ASD relay is getting power and after swapping another one in from my other jeep no difference made. i have probed my injector plus I'm getting a solid ground but no alternating power. I've also cleaned all my grounds no difference made. Any ideas? I'm a 19-year-old kid who wants his car back lmao.

tjwalker

If your engine runs with starting fluid, you have verified that the spark part of the equation is okay. You have a "fuel delivery" problem. Just knowing there is fuel pressure at the rail isn't enough. You must use a fuel pressure gauge and see how much pressure you have. For a 2000, you need 49.2 psi plus or minus 5 psi for your engine to run. Proper pressure is critical here.

Start there. If you don't have access to a fuel pressure gauge, they can be rented inexpensively from many parts stores. Call around for availability.

Good luck and keep us updated!

robsjeep

Ok, so you say the injectors are not firing, confirmed by probing. How were they probed, what where the results, what meter settings, digital or analog meter, or a scope? (remember you are measuring a rapidly switching dc signal )

Please be very very careful when probing any of the injection stuff. An accidental short of an injector while probing can fry the scr in the ecu brain. The scr is a semiconductor "relay" that switches the injector power. Use of the ohm meter is also dangerous as the ohm meter sends power from the meter INTO the circuit you are probing, This can some time fry injection parts, avoid ohm tests on the harness if the ecu is plugged in unless you KNOW that particular wire is safe to probe.

I once fried my brain, It was decades ago. I wont do that again, duh, learnt me leason well. She blowed the scr when I accidentally missed probed injector cable, old Bosch D-Jetronic Porsche. (D-jetronic, or D-Jet is one of the earliest mass produced electronic injection systems, back in late 1960s early 70s lot of VW Squarebacks had a similar D-Jet, detuned for a different motor verses the Porsche, then Bosch came out with the L-jet, (I dont know what happened with E, F, G, H, I, J, or K ) Fortunately used brains back then were common and cheap at the wreckers. I still have that fried brain. All it needs is a new scr soldered to the board. No integrated circuits, all individual transistors soldered onto a very large and crowded board. Low tech.

Be like a doctor, Do No Harm, use care when you probe.

Anyway, let us know what you probed.. Voltage maybe at injector plug while cranking?

Of course examine the harness through out the engine bay for damage, check the engine sensor connectors, both electrical and vacuum hoses. There are some on the air intake, wires and vacuum hoses. And there is the mps, (or Manifold Pressure Sensor) is mounted high up middle of firewall above the rear of the valve cover The mps has a vacuum hose and wire connector, make sure nothing is loose, torn, leaky etc...



Also did this problem first happen after some incident or work done on the rig?

Also since I assume you have been cranking the motor a LOT, the battery is low, you so if you got a charger, plug it in so you dont end up dead. No not you, that is figurative speak, I mean the battery dead. you wont be able to do diagnostics nor testing with a dead battery, and a battery sitting at any less than full charge is harmful to battery life. Treat a battery well.

As for pressure but no flow of gasoline, Other poster is correct. You may have an obstruction after the pump that wont pass hardly any fuel, but can build pressure past it through what gets by it. . You want to see the proper pressure MAINTAINED while running, and I mean while running on the injectors, NOT on starting fluid down the intake. If the injectors start to open, and there is an obstruction upstream you will see a big pressure drop down stream of the obstruction at the injector when the injector opens, which WILL result in pressure loss at open injector, and a dribble rather than a spray pattern of fuel, and maybe not enough fuel if obstruction is bad enough. Flow or Volume verses Pressure, you need both, and having one don't mean you have the other unless you are operating the injectors while reading the pressure.

Anyway if indeed injectors are not firing, do a visual on the electric and vacuum hose bits. Check the easy stuff first.

http://cruiser54.com/

The above link, it has a lot of good jeep xj electric info. The guy that runs that link is a contributor here, held in wide regard.

Post more and we can go down what ever diagnostic rabbit hole we need too. I am myself more versed in the Renix injection system than what you got going on in your 2000 jeep. But lotta folks here know your system well indeed.

So give us the details on your injector probe tests, describe if any incident might be related to when this issue started (Not started issue is more like it).
And report back on the once over of the hoses and wires.

I was older than you when I got my first brain. Cut me teeth you know on carburetors, and breaker point ignitions, Back then you know all was good if you had dual carbs AND a dual point set up. Then one dark day they came out with the new whipper snapper de-carburetroed cars, with electrons flowing every place. I had to learn to figure them out or become a relic of the past. Today cars dont even have keys to open them nor even start them, we are living some crazy times.

Good Luck!

DavesJeep101

Correct, don't probe with an ohm meter. The system does not pulse power, it switches the ground on and off. The power to all injectors should be battery voltage and consistent. Get a cheap set of Noid lights for testing or you can fry the brain.

robsjeep

Yeah, a lot of cars have dome lights wired like them injectors, non switched positive, and switched negative wire from the door switches to turn the light on when the door opens.

lawsoncl

Yes. The 1991-2001 engine computers control the ground. The positive to the injectors comes from the ASD relay.
The older Renix pre-91 computers and wiring switched the positive wires, and the grounds all connect by the dipstick.

(added that info for future searchers, who may not realize that changed)

KadeH

I will go rent a fuel pressure tester tomorrow and report back thanks for the help man. directed at TJwalker

KadeH

It randomly died on my trip To Ventura back to riverside on the freeway at that point it died and instantly turned back one after a key turn. nothing out of the ordinary at the time of this happening. i probed the injector plug by grounding my multimeter that was on 20A DCV onto my battery then sticking in the positive side into the plug no power getting to them while the car was getting cranked. probable bad looking back on it but i did it vise versa with positive and probed with the negative got a Solid ground.( was digital meter very old devise but seems pretty accurate) I also have been trickle charging my battery at night for this reason that you noted. i Will be pressure testing come tomorrow and will write back problem is I don't know if i will be able to get the car to start on fuel injectors to see if my fuel pressure will drop. only code i had before all this happened was a (small evap leak) wish i had the code but done remember also had a code for a misfire on cylinder 6,5,3 but seemed to only be at low temperatures my cold starts sounded and felt like a 7.3 in the dead of winter.

robsjeep

Although it is true that the injectors are "DC", there is a BIG alternating part to it. This is because the DC signal is switching so fast. A digital meter when set to DC cant really read it correctly. The signal is actually off much of the time. you can get nonsense readings. The AC setting on the meter are designed to give the rms value (root mean square) of AC that is a smooth sign wave. rms is not the peak, nor is it the average ( for AC average volts over time is zero between the wires!) This wont work correctly either for the non sine wave pulses of the injector signal.
An analog meter at least you can see the injector signal pulse, see the needle twitch. you have have to set it to a lower than 12 volt range to see the needle twitch or not in a uniform fashion. It is very hard to discern this pulse properly on a digital volt meter.
Ideally you use a scope, which will trace a line of the voltage up and down over time as the voltage goes up and down

One of the injector pins should have positive power when engine is on. other pin will be a pulsing ground. NEVER USE YOUR OHM METER ON THE CONNECTOR TO THE WIRE HARNESS. you may safely ohm test the injector itself, across its two pins, ONLY if unplugged from harness. You typically do this to test the ohms resistance of the magnetic coil in the injector, but never with the injector connected to the harness for this test. But you are not suspected a bad injector coil, much less all six being bad.

To test for the negative injector pulse in harness, use DC analog meter..... positive lead to positive batter post. Negative lead to negative terminal on injector harness plug. Have ignition switched on and off, crank engine. You should see the needle twitch. you may have to reduce the DC volt range if you dont see any twitch at 12 volt range.