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TPS ? Fuel Pressure ? What You think ?

It isn’t that any gauge needs a snubber by its design.
Pump design can be smooth or create pulses. Gear driven pumps are smooth, oscillating pump like the back and forth solenoid factory pump create massive pulses.
The snubber when needed is both so you can just read the average of the pulse and to protect the gauge.
 
thinking about Glow Shift gauges... the fuel pressure gauge that was in the 93 is a mechanical GS gauge that is liquid filled. I have it cobbled up on the 95 for a boost gauge since I had lost my boost gauge when I replaced the dash. it reads 3 psi now with the engine off!! not accurate at all.

btw I actually found the missing boost gauge hiding in my garage the other day and will be installing it in the 95 soon. just thought I'd share the accuracy on the GS gauges I experienced. I need to put another gauge on the 93 and see what the fuel pressure really is now that I see this gauge was off by that much. when it was connected with a live fuel line in the cab it always showed 8-9 psi when running, never moved even under load. I bet I was only getting a max if 5 psi idle and much less under load!
 
Will L. said:
It isn’t that any gauge needs a snubber by its design.
Pump design can be smooth or create pulses. Gear driven pumps are smooth, oscillating pump like the back and forth solenoid factory pump create massive pulses.
The snubber when needed is both so you can just read the average of the pulse and to protect the gauge.
Click to expand...
I believe this is a gear pump. Carter that Leroy furnished with the relay/prime button harness for the 2000 year truck.
 
This morning made a run to the fillumup station with two five gallon gasoline jugs.
Got the jugs filled and was headed to NAPA for some vacuum hose and a adapter.
Got a couple blocks from the fueling station and truck totally died. FP was zero. Got coasted to duh curb.
Turned off ignition switch, back to run position, no fuel pressure and no start, enjun did crank over.
Let it set for an eternity( three, maybe four minutes, key to wait to start, cranked it over and fires up.
Into gear, a little throttle and enjun dies, no FP.
Set for a little longer, key on, wait to start and engine fires up. Make it about four blocks towards home, dies again. About a ten minute wait, engine then starts and I make it home.
This is the message I get when I plug in the Autel AP200.
IMG_0198.png
Let it hoover on that for about twenty minutes then shut it all down.
Moved the truck so its not in the way and send @Quadstar Tuning LLC an email.
Going to get a tuned ECM.
Hope that fixes the problem.
Too tired to screw with it for now. If there is any more diagnostics to be performed it will have to wait.
 
I wonder if the ECM is loosing power or ground from somewhere. you can easily check by probing out the connector under the dash according to the pinout for power and ground. could also be a connector somewhere too that has some corrosion.

Check the cigar plug fuse! I have seen where that one fuse GM piggybacked off from to provide power to something essential.
 
@MrMarty51 re your number 20 post - The last time I used a pump like that to drop to quadrajet pressure I had to use a by pass type regulator back to the tank. That would mean adding a return line to the tank. You cannot really easily tap into the diesel return line with risking plugging the return from the IP. After a certain pressure certain regulators do not work. Can't help you further - would not use that kind and high of pressure capable pump. You are on your own.
 
MrMarty51 said:
Going to get a tuned ECM.
Hope that fixes the problem.
Too tired to screw with it for now. If there is any more diagnostics to be performed it will have to wait.
Click to expand...

Save your money. It's likely not the ECM. You are loosing power to the ECM either by bad ground or bad +12V to the ECM. A connector problem at the ECM could be hidden for a time by swapping the ECM till it comes back.

As it's acting up, now, you should verify voltage to the ECM.

If you must unload the parts cannon and re-load with an ignition switch. Otherwise you have a real PIA of an intermittent electrical connection to hunt down. The kind that doom the electric vehicle utopia... Regardless IF you change the ignition switch take apart the old one and inspect the contacts for burning to confirm if it's the problem.
 
royunion said:
@MrMarty51 re your number 20 post - The last time I used a pump like that to drop to quadrajet pressure I had to use a by pass type regulator back to the tank. That would mean adding a return line to the tank. You cannot really easily tap into the diesel return line with risking plugging the return from the IP. After a certain pressure certain regulators do not work. Can't help you further - would not use that kind and high of pressure capable pump. You are on your own.
Click to expand...
Yup, After looking at that FP regulator I realized it required the return line and most likely would not work unless I would run a separate pipe back to the tank.
I had that regulator when I was doing an experimental FI system on my 78 MG-B roadster. That system I could not get it functional and so dismantled it and went with twin SUs instead. Thats whats on the car now, with a proper PSI fuel pump for those carbs.
I did plumb in a real nice fuel return pipe back to the tank filler neck and I will someday purchase the Patten Machine Products fuel injection system but my truck takes priority over all else.
 
WarWagon said:
Save your money. It's likely not the ECM. You are loosing power to the ECM either by bad ground or bad +12V to the ECM. A connector problem at the ECM could be hidden for a time by swapping the ECM till it comes back.

As it's acting up, now, you should verify voltage to the ECM.

If you must unload the parts cannon and re-load with an ignition switch. Otherwise you have a real PIA of an intermittent electrical connection to hunt down. The kind that doom the electric vehicle utopia... Regardless IF you change the ignition switch take apart the old one and inspect the contacts for burning to confirm if it's the problem.
Click to expand...
Yup.
I do want a tuned to my equipment ECM but I will do whats necessary to find the problem too.
The temps over here has been in the 100s, 110s and cooler days are coming this week. I just hope that there is not a lot of rain with it.
I want to be able to crawl around that truck without looking like a drowned rat. 😹😹😹
When I was having boost problems, every terminal plug I could get to was taken apart. I used one of those root canal files and scrubbed every connector clean, then, I used a very light smear of this Truck Lite corrosion preventive compound on every connector.
I would hope that stuff holds to its reputation and keeps any corrosion from building on any of the connections.
I did not, at that time, do anything under the drivers side of the under dash components.
I will though start on the passenger side and remove the jockey box and pull all of the connectors from the ECM and have a look at those. Get out those dental files and shine things up once again.
Probably do as You suggest and pull that ignition switch and check it for burnt connections.
 
WarWagon said:
Get a voltmeter on the ECM power and ground pins esp if it's broken now. Back probe em.
Click to expand...
I do have a Mac Tools back probe kit.
I will get that done.
Maybe even stop at the store and pick up an extra multimeter so with a freeze frame and then drive until it stalls again.
Keep both multimeters visible so when the engine kills a quick visual and the culprit can be seen.
 
Pulled the ECM this morning.
Temps has dropped nicely. 52 degrees here.
Was ISO of corroded pin terminals and found nothing that would obviously create a problem.
Now there is room to get in there and file the terminals within the connectors.
One thing I am not certain of is the two black spots on the top of the box.
Almost appears to me to be marks created by hot spots.
What say You guys ?
I did use a slight amount of B&P cleaner to wipe off some dirt and oily looking residue.IMG_0223.jpeg
 
Those are what looks like rub marks on the aluminum casing. nothing to worry about. if the contact pins are clean I would only apply some bulb grease and re-install. check for power and grounds with the key on, also verify you are still with no communication to read codes

if all powers and grounds are good. then move on to checking your 5v+ reference voltage from various sensors. there will be two or three different pins on the ECM that will provide 5v+ out to various sensors. if any one if them are shorted, it can cause chaos. problem can be in the harness or internally in any one of the sensors.
 
dbrannon79 said:
Those are what looks like rub marks on the aluminum casing. nothing to worry about. if the contact pins are clean I would only apply some bulb grease and re-install. check for power and grounds with the key on, also verify you are still with no communication to read codes

if all powers and grounds are good. then move on to checking your 5v+ reference voltage from various sensors. there will be two or three different pins on the ECM that will provide 5v+ out to various sensors. if any one if them are shorted, it can cause chaos. problem can be in the harness or internally in any one of the sensors.
Click to expand...
Before trundling offt to working.
Stepped back out to the truck for a second look above the area where the ECM resides.
There is plenty of room above the ECM and there is no wires or such hanging.
The two black spots have no rub marks within their boundaries.
Thinking I’ll pull the cover for a looksee.
I will not however stop at this.
I will be hooking back up the battery cables and checking for proper voltages to the pins within the connectors, and ohms test the grounds too.
 
IMG_0224.jpegIMG_0225.jpegNo burns or bad spots within.
There is not one thing in the upper regions of the placement of the ECM that would have made rub marks on that cover.
ONWARDS ! ! ! !
After work that is. 😹😹😹
 
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