Thanks mikeyB, That 'll do!


OK, long day, did the complete procedure outlined above, and I have acouple questions,,,?

Since this is the first step,, what is "Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)"....?

Second let me say the truck is not throwin codes, I'm still doin this to cure a low rail pressure off idle, (Idle is 6,500-7,500)as measured by my scanner,,,the parameters that I can see seem good, absolute throttle position,barr press, Map pressure, outside temp, IAT, rpm, %load,coolant temp, fuel level,,,,fuel pressure not so much.

In addition there seems to be no difference in readings weather I use my old RPS vs the new one,,which I bought because I was having a persistant 0192.

But I still don't 'read' any higher than 9,500psi and that is only consistant at about 30-40mph under light load..after that it's all over the place mostly between 4-9,000,

Starts good, sounds good, smooth across the board,no surging, absolutly no smoke, new 50 sticks,cp3, fca,PLV, and rps?

all that being said, and omitting step one above, I went right down the list, got to step 3 and it of course threw 0193! =replace sensor. Continued down the list, good,good,good, got to #8 had 60Kohms, got to #9 had 16Kohms,,
SIGNAL& 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND?

How the ef ru gonna find that!!??

I'm spent...

 

I did note that the cam sensor is on the same circuit and I wanted to clean the connection but I couldn't unlock the clip! urgh!

 

Can someone tell me if on a good running truck, if u unplug, replug the fuel sensor do u get p0193, or the fact that I do suggest a definatively bad sensor?

Thanks,

Ignition on, not running as/per step#3 above...

 

studied the wiring diagrams and the circuit for the FPS is pretty short, I managed to find all the ends for the 5v supply, and the signal wire goes right to the ECM. Testing for short to ground found there is no short to ground when the ECM is unpluged. cleaned the grounds on the ecm plate and no improvement,

Still would like to know about the plug and unplug results for a known good FPS,,,

Any help or ideas would be greatly appreciated.

 

What are you using for a scanner? I've got a Genisys Evo and its having problems reading the rail pressure on my 2003.

 

I borrowed the scanner,,I think it's an actron cp9175 obdII,,,

....Can someone tell me if on a good running truck, if u unplug, replug the fuel sensor do u get p0193, or the fact that I do suggest a definatively bad sensor?

Thanks,

Ignition on, not running as/per step#3 above...

 

Got hold of another truck today, same year, same tranny, box stock. hooked the scanner up, and yes if you plug, un plug the rail pressure sensor, ignition on not running, it throws a p0193,,,and goin down the road showed the same pressure readings,,way off.

Soo,, along with cLYAH I suspected the scanner,,,Got ahold of a pc version of Auto Enginuity obd II scan tool and low and behold 6500-7000 psi at idle 14k-18k from 30-60mph depending on load and upto 24.2K at wot!!!

I think the actron scanner was actually screwing it up, because it sure felt stronger with the Auto Enginuity scan tool hooked up.

Interesting that it still failed resistance test to ground, as well as the p0193 code which suggested the pressure sensor was bad,,,?

we'll see,,,so far no codes, and it seems to run strong for a stock tune,,still I would expect a little smoke for 50hp injectors and other mods, but again, we'll see.

so for now, it's reading fixed!

Thanks to all who commented!

I'm goin to sleep well tonight!!

 

got my 2nd wind..so I thought i'd post a pic



'78 xs