P0093

TKB4 · **Posted:** Thu Aug 01, 2019 6:17 pm

I just put new head gasket and ARP s and exhaust valves with different head that was checked out ok, rockers and TB maintenance with new water pump and Lift pump facet type under battery tray for now and new fuel head and filter. I did not replace fuel line back to tank at least not yet. ( This jeep was bought as salvage for body parts 2 years ago it had been overheated and had busted hoses and thermostat plastic pieces cracked and the radiator showed signs of previous owner trying liquid glass type head gasket sealant. I couldn't resist trying to get it running which I did back then but had other projects and it had steering fluid leak bad tires etc so since another one dropped valve recently I decided on trying to resurrect this one again.)

After verifying the timing a couple of times I tried to start it and no go , fuel head pump soft thus added lift pump and cracked fuel rail fittings from CP3 to rail and number 1 through 4 injectors 4 being last and bleed till fuel consistently present. Now pumps up very tight but catcher is it still doesn't start and it has a check engine light on all the time. I read codes and come up with the P0093 which is stated as large fuel leak. if cleared about half the time when trying to crank it will still show CEL but when read it says Pass sometimes 3 times in a row Then the P0093 returns.

I tried several things. I avoided ether but I did try wd40 in intake that seemed to be sucking adequately and it started for a few seconds thus in my mind verifying that timing and rockers and valves are ok. This confirms to me it is a fueling problem. I checked noid lights and nothing but I recently showed that initial cranking on normal running CRD does not show on noid light , so not very helpful. At some point my son dropped an injector in moving things around but he didn't see anything wrong with it and put it back and doesn't know for sure which one it was. I also broke the tip off number 4 fuel return fitting so cannot lock it down with the clip. I tapped on metal part of injector head to see if it would possibly unstick an injector . No change. I also unplugged them and turned engine over and no change.

I am considering changing out all four injectors with a different running jeep to rule out injectors. I have also considered changing out the crank position sensor.

So the code clears but check engine light never goes away maybe indicating a code my scanner cannot read like transmission code etc. ? anything to do with no fuel? The fuel primer staying very firm seems to indicate there is no fuel leak. The fuel quantity solenoid was unplugged cleaned and replaced and the back fuel rail sensor has been removed and swapped with no 4 injector plug with no change and then swapped back since I was sure it was originally correct. I also put fresh fuel in filter and replaced.

I have researched the P0093 threads and several seem to be related to air in fuel alone with other causes such as bad fuel quantity solenoid.

!. Will broken fuel return tab on number four injector cause a no start or just leak fuel after running?
2. Any way to prove Fuel quantity solenoid functional without replacing ?
3. Why is CEL on even when passes code reading?
4. Do I need to replace fuel return tab before proceeding?
5. Would you swap injectors next?
6. Any other suggestions? I am taking a break on it to reflect. It would be nice to know actual fuel rail pressure .

flash7210 · **Posted:** Thu Aug 01, 2019 8:30 pm

What tab is broken on the injector?

Have you tried cracking open a injector line to bleed the air out of the rail?

A p0093 could also indicate a problem with the rail pressure sensor.
After you feel confident about bleeding the air from the rail, disconnect the pressure sensor and try cranking the engine.
Also scan for codes again to see if you get a different code.

It still no luck, reconnect the sensor and unplug the fuel quantity solenoid on the injection pump. This will divert all fuel up to the rail.

TKB4 · **Posted:** Thu Aug 01, 2019 8:49 pm

Thanks flash
The tab thats broken is the part that pushes in top of injector for the fuel return line .Guess they got hot and old and brittle. None of them could be pushed in just with hand pressure had to tap lightly but guess number 4 was a little crooked and tip broke off.

Yes , I have cracked open all the injector lines closest number one first then in order till number 4
Will give those steps a try and post results !

TKB4 · **Posted:** Thu Aug 01, 2019 10:38 pm

When I removed the fuel rail sensor connection and cranked it did not start and there were no codes.

I then replaced the fuel rail pressure sensor connector and removed the Fuel Quantity solenoid connector. It did not start with this removed . I checked for codes and got P0090 which is open circuit for the FQS and this is to be expected.

flash7210 · **Posted:** Fri Aug 02, 2019 8:26 am

Disconnecting the pressure sensor should have set a code. Either a p0093 or p0193.

If you have a scan tool that can read fuel rail pressure, check what the pressure is while cranking.
Of course, the sensor will need to be connected for that to work.
With the sensor unplugged it should read ~26000 psi.

Keep trying with the FQS unplugged. I've had issues with it before and the engine will start, run, and can be driven but will be in limp mode.

TKB4 · **Posted:** Fri Aug 02, 2019 12:34 pm

Should it start and run in limp mode with both sensors unplugged ? I still have the FQS unplugged.

I know that all the wiring harnsees may not be identical but the plug for injectors and the plug for fuel rail pressure are interchangeable and I have swapped them but I didn't swap them with each try of the fuel sensors FQS and Rail pressure. My number 4 injector electrical connection comes from wiring harness by itself. The cam sensor and fuel rail sensor comes from wiring harness together and then separates. I looked at 2 others of mine and they are same way.

Does anyone have one that the connector for #4 injector is with the sensor for the cam position sensor for a couple of inches before splitting to separate wiring?

Will try again later today and see what happens and may swap #4 injector connector with fuel rail pressure sensor again.

TKB4 · **Posted:** Fri Aug 02, 2019 2:37 pm

Well must have been a bad connection somewhere or maybe some more air in fuel supply but I doubt that.. I just unplugged and replaced all injectors and cam and fuel rail pressure sensor and fuel quantity sensor and it fired up !!! Now to put external timing cover and accessory drives and rest on and take it for a spin!! Thanks for the advice and possibly some divine intervention !!

P0093

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