Check my work re: Fuel pump failure?

[Straylight]

Hey guys!

It's been a banner trip across the country this week. I'm currently at a repair shop in Cheyenne, WY, waiting on fuel pump replacement to commence tomorrow morning. I'm pretty sure I've got a failing fuel pump, but I'd love a second opinion.

Specs:
1999 Chevy Express 3500, 7.4L Vortec V8 engine. Fleetwood Jamboree 22C built on the cutaway chassis. 65k miles on the clock, but not well maintained by POs.

Recent Work:
New battery, new starter, freshly polished main ground (had starting issues earlier in the week, slow crank no start; I went through a battery and starter before I thought to have the mechanic check the main ground). This was during the current trip.

Had a no crank no start, before trip; mechanic found broken wires and soldered them. I believe the prior (bad and dishonest) mechanic replaced the ignition coil, the distributor cap, and MAYBE the crankshaft position sensor before he decided to stop hanging parts on it and take it to a better mechanic (who found the wires).

Recent Symptoms:
Rig ran great other than the slow crank, and after we fixed the main ground it started right up and again ran great. This trip has been 1500+ miles in a few days, mostly on cruise control around 62 mph. I noticed a slow start sometime after we fixed the slow crank; that is, cranking quickly and nicely, but not firing for a while. I stopped at a gas station, filled up 8 gallons, went to start, and it just cranked. It seemed like a fuel delivery problem. I had an auto parts store bring me a new relay and fuel filter, popped both in, got it to start but it was still sluggish to do so.

I had been noticing the cruise control would hiccup every once in a while, almost as if I had cycled it off and on for a second. Maybe twice in 1000 miles. This began to happen with more frequency after the gas station and the relay/filter replacement. It started to get pretty frequent (three times in 100 miles). Eventually, I stopped for the night and decided to have it looked at in the morning.

It continued to start slower than I'd like. On my way to the first shop (they said I was too tall to fit on their lift) I did not use cruise control, but I lost engine power five times in 3 miles, just like I had taken my foot off the accelerator. Electronics were fine, no CEL, didn't need to pull over and restart; just had times when it slowed down and nothing I did would give it more power, and after a few seconds it would surge forward and be fine. Engine has been running a little tougher and jumpier than normal, which is to say that it's never rough and jumpy but it has been since the gas station incident.

My oil pressure gauge has been reading higher than normal since I stopped for the night and then drove it to my two shops. My temperature has been fine. My fuel gauge has been broken for about three weeks, stuck on empty. I do not have a CEL and have not had one for the duration of these symptoms.

I have stabilized every drop of gasoline on this trip with StaBil, 1 oz per 5 gal, per the recommendation in my thread about my generator. It also got a half can of SeaFoam at the start of the trip. I have used one can of GumOut mid trip, before these symptoms, hoping to remove what I thought might be varnish on the part of the fuel pump that senses fuel level. Oil change is recent, fewer than 3000 miles, with a NAPA Gold filter and full synthetic oil. Newest fuel filter is a Wix.

My Take:
The fuel gauge failure, lovely crank but sluggish start (if it starts at all), rough running, and intermittent engine power loss with increasing frequency all point to a progressive failure of the combined fuel pump/sending unit. I suspect that the oil pressure has increased because the engine has been working extra hard in the absence of steady fuel supply.

It seems as if some of these symptoms could come from a bad crankshaft position sensor, and I also recognize that I might have a blind spot regarding another cause.

Any thoughts?

[TakingThe5th]

I had a similar situation with an older step van that had set around a lot and the problem turned out to be junk in the gas tank, specifically somewhat large rusty pieces of metal in the tank that would partially block the inlet at times. I had to remove the tank and shake it out and removed the fuel pump and decided to replace it as well. There was also an inlet screen that I either blew out or replaced (can’t recall which).

[Gjac]

I had a failing fuel pump on a trip out west last year that just got progressively worst as the trip went on. Checked fuel pressure and it was within spec so I thought the fuel pump was good, so after changing wires and a bunch of ignition parts I took it to a shop. They were stumped also and thought it was a bad timing gear at first because the fuel pressure check out fine for them also. The thing I learned was there is a flow rate spec also that is needed to deliver fuel to the engine. Its kind of like volts and amps, just because you read good volts does not mean the proper amps are getting through. An easy way to tell if it is the fuel pump is to spray starting fluid or gas into the TB and if it keeps running it is probably your fuel pump.

[blownstang01]

What were the 2 wires that were "broken" ? Mice ? It could be additional wiring issues. The crank sensors are real fussy with radio interference, and if you're having wiring problems it can cause all kinds of problems like you describe. As said above, the only real way to determine a fuel delivery issue would be to hook up a fuel pressure gauge so you can read it while the problem is happening. Oil pressure will not increase due to the engine "working extra hard", the oil pump spins in relation to RPM regardless of load. Is it possible once the issue arose you are looking at the gauge more closely and feel the pressure is higher ? The only things that would really cause an oil pressure rise, is a plugged oil filter with a stuck bypass(highly unlikely), or a stuck bypass in the oil pump itself...again unlikely unless maintenance has been really poor. I suspect an issue with the gauge as you are already having problems with the fuel gauge....again maybe an electrical gremlin ?
Good Luck

[Bessie-Hunter]

Check the fuel pressure first. Low fuel pressure will cause loss of power and extended cranking time.