Engine/Transmission (1998.5 - 2002) Pre FP normal, Post FP dropping?

[rweis]

16k miles, pre & post FP. Pre FP holds 14psi under just about any condition. Post FP USED to be about 1 psi less up until about 200 miles ago. Went to 2psi less. Now 3 psi less. Changed fuel filter thinking it was clogged, nope that's not it. No change in differential.



USED to NOT be able to pull post FP below 12psi. Now can pull it to 8psi with pre FP still 14psi.



If LP wouldn't pre FP drop off as well? LP by tank and can hear it running, but know they have many other symptoms for failure.



No hesitation on acceleration, can wind up to 2700 no problem, no stumbling.



Have not swapped sensors yet, but that's my next approach unless someone's got some other ideas?



Bob Weis

 

[illflem]

It very well be that your pre-filter sender is the one going out. Before I gave up and went with mechanical gauges every sender failure I had resulted in the gauge only reading the pressure it saw most often and zero, no in-between. Can definitely lead you into a false sense of security...

 

[rweis]

This week I will dig into tightness of couplings, swap sensors, etc.



I'll let you know how it goes. Sensors are suppose to be solid state and lifetime warrantee.



Might need to "press to test" that.



Bob Weis

 

[15w40]

The Westach solid-state senders are sensitive to a few unique problems that do not affect the resistive senders. The three-wire sender requires a precise 5-volt DC supply, usually derived from the gauge. If the 5-volt supply were low it would appear as if the pressure is low. The green signal lead must see an electrical load of 50K ohms. If for some reason the electrical load is less then 50 K ohms, the gauge will read low. Check for a good (accurate) 5 volts between the red and black leads and check for moisture or dirt on the leads from the sender to gauge.

 

[rweis]

Ah Ha,



TDR is unbelievable! I will check that, very plausable possible problem.



I was going to call Westach in the morning, but will check 5v between red and black first. And will clean the contacts between the sender and the gauge. For the gauges I run a dedicated ground back to the battery and a dedicated 12 volt circuit off of a Painless (ACC / RUN) 7 circuit add on.



Any suggestions other than air and a little contact cleaner for the contacts? Where do guys get this dielectric grease? NAPA? Radio Shack?



I went under the hood and checked for fuel leaks specifically in the gauge system because that would cause an erronerous reading. All was tight and clean.



I leave for a week in TN on this comming sat and would like to clear this up before then.



Thanks,



Bob Weis

 

[BV]

dielectric grease

Should be able to buy it at the local auto parts store - Permatex pn: 81150 DIELECTRIC GREASE



Good Luck

 

[rweis]

For Westach owners, I emailed them and a very easy procedure to check the mechanism. Their response was very quick email.



0psi = 0. 5 volt



Full scale = 4. 5 volt



red to black = 5 volts



mid scale = 2. 25 volts



Bob Weis

 

[rweis]

Checked the voltages, all ok.



Called Westach, switched the sensors, problem followed the sensor. They are going to put a sensor in the mail this am. Excellant customer service!



THE reason Iwent with Westach was the durability of the solid state sensor. It MIGHT be that the VP got through to the sensor. I had an 18" snubber hose and a needle valve almost shut off trying to protect the sensor.



After I get some time on the new sensor ( 1 yr) I'll bring this thread back up and let you know how it went.



Bob Weis



Bill,



LP side FP, and OP still functioning fine, maybe a bad sensor, maybe VP can only be monitored successfully by mechanical gauge?

 

[OL RATLR]

gauges

Go Mechanical no more problems. :--) Norm