Truck Starts Consistently But Not Like It Should

downplay411

This truck starts every time but I either have to turn it over once, stop, and then turn it over again to start, or on the first time, it will spudder weakly a little, then fire up. Once in a while
it will just turn over strong on the first try but not often.

It now has a brand new alternator, new spark plugs, a new fuel filter, and a new air filter at 144,000 miles. The plugs and filters were overdue. It starts just the same before these updates and after.

The battery only has about 7 months left on it but it shows good on 2 different testers.

Any ideas or suggestions?

As another symptom, it also seems to have slight power loss beginning at about 50 mph+ but it will go up to any speed, not too big of a deal.

Although, this may have changed with the spark plug replacement. I drove it today up to
55 mph and it did not have the loss/shudder feel at 50 and the check engine light did not
come on. Before the new plugs, the light came on almost every time I drove it at any speed. I'll have to drive it some more to see if this has really changed permanently.

ray80

Cold winter temps where you are? Does it turn over quickly and maybe just not fire right away? Battery may show ok but if its old cold starting may stress it a lot. 14 year old vehicle that had overdue plugs and was running perhaps a tad rough, cat converter ever changed?

downplay411

The temps are very up and down here in NE Oklahoma. We have had a couple of sharp cold spells this season. The high is gonna be 55F today.

It always turns over immediately, it just doesn't fire immediately most of the time, until I stop and turn it over again. Like I said sometimes it will chug a moment, then fire on the first try. And then on the odd occasion it will fire immediately like it is supposed to. Please forgive my misuse of terminology, I'm just learning to be my own mechanic.

It runs pretty well, sounds mostly smooth once it starts. Sometimes it has a slight tapping/ticking noise that is new but it doesn't sound awful. A mechanic said it didn't worry him too much. It hasn't always had proper maintenance though. My grandfather was driving it while he was getting Alzheimer's and dementia, so it is hard to say how much it has been neglected. I don't think the plugs or fuel filter were ever changed until now.

You mean catalytic converter? Does that affect the starting? Isn't that related to the exhaust? They get clogged up and hinder the engine exhaling?

Could it be the spark plug wires? There was a tiny bit of corrosion on the wire side, on one side of the engine.

What about the ignition coil?

Thanks!

downplay411

As it turns out, I think it is a fuel pressure problem.

I got on Youtube and watched some good videos on how to perform pressure tests.

When I turn the key on (but not the engine) the pressure quickly jumps up to over 50 PSI. But then it very rapidly falls back down to below 10 within just a few seconds.

The same thing happens after the engine is running and I turn the key off. Is this supposed to happen?

It seemed to have the proper pressure while idling, at a constant rev, at quick revs, with the fuel pressure regulator on, and with the fuel pressure regulator off (where it just jumped up slightly). It never went super high or super low during the running tests but stayed in a pretty narrow range around 43 PSI. There was also no fuel in the pressure regulator, in the vacuum tube, and it seemed to have a strong, steady vacuum.

Since it is only losing pressure with the engine off, but pump on, and it happens rapidly, this has to be the check valve in the fuel pump, correct?

Thanks!