peterbilt385

I have a 1990 dlx 4x4 p/u with a reman 22re. When the engine was installed all worked fine. I have developed a problem where the truck starts fine when cold then if \when shut off it will not restart until it cools down. There is spark. The whole fuel system has been replaced new pump, relays, fpr, filter, ect. any ideas would be appreciated.

Co_94_PU

iTrader: (-1)

Start with checking easy things.
Are your temp sensors accurate? (Do they need cleaned, replaced, or are there wiring issue like frayed wires, damaged insulation, disconnected or loose fitting connectors)

Is the spark consistent hot vs cold. (With a spark gap tester the spark should have the same color profile)

What, if any, difference are you seeing in the fuel pressure?

scope103

I'd also look at the Fuel Pressure-up system: http://web.archive.org/web/201501160...ne/41fuelp.pdf It's designed to address vapor lock by raising the rail pressure under certain circumstances.

snippits

Next time you get the engine hot. Unplug the electrical connector to the cold start injector, and then try to crank it.

RAD4Runner

O.P,,
Here's how we (Wallytoo, me, et al) installed fuel pressure gage to monitor rail pressure: https://www.yotatech.com/forums/f199...l#post52312190
Video on post shows how rail pressure varies when VSV comes on or off, exposing FPRegulator to intake vacuum OR atmosphere (I simulated but unplugging intake vacuum line that connects between FPRegulator and and VSV).

Also, because problem seems to be temp-related, I suggest you inspect and clean all your temp senders, AND MOUNTING THREADS to bare shiny metal.. That should be done at least once every 29 years

AppalachianOffRoader

Just curious. I'm having the same exact issue with my 92 pickup.

RAD4Runner

Did you try what have been mentioned above?

wallytoo

iTrader: (1)

no kidding, right?

AppalachianOffRoader

"dID yOu TRy aLL tHE OtHeR sTUfF i sAiD"

Yeah, dude. I tried all the above mentioned things. In fact, I did all these things before I commented, because I followed the charts in my FSM

Obviously, I'm overlooking something.

Did you fix the problem? Or are you deflecting because your ˟˟˟˟ isn't actually fixed yet?

RAD4Runner

You did not tell us, so I asked. Fair enough?

I don't know about the O.P.'s, but, yes, my truck is fixed, but it still looks like **** LOL!

wallytoo

iTrader: (1)

deflecting? hardly. my 22re runs excellently. used the pressure gauge to help diagnose fuel system issues, and to avoid replacing perfectly good parts with new parts that weren’t needed.

what does your pressure gauge read while your engine is running?

vintageracer

I had this exact same problem 30+ years ago with an early 1980's E350 Ford 4WD van. Start easily cold and run for about 20 minutes and then would not restart.

I tried EVERYTHING mentioned above and then some. Fuel system filters, fuel pumps, electrical grounds, gnition parts, distributor etc.

Ultimately I found one wire in a loom of several wires that ran across the intake manifold under the carburetor that was missing a 1 inch section of wire insulation on 1 particular wire. That 1 wire was part of the Dura-Spark ignition system. The wire insulation in that high heat area under/around the carburetor was super brittle due to all the heat cycles experienced over the years just cracked and fell off the wire in that particular section of wire.

When the van engine got hot there was enough heat added to the wire through the 1 inch section of the wire with no insulation the would create enough resistance within the wire that the electrical current would not flow through the wire. Therefore the NO START condition.

Remember Voltage = Current X Resistance (V=I x R). Heat can build resistance within a wire. I cut the wire to remove the section of wire with no insulation and properly spliced the wire with heat shrink insulation over the repair.

PROBLEM SOLVED!

I never had another issue with the van.

Given the fact that you stated this problem developed AFTER you installed the new engine in your truck can very well mean the problem IS in the wiring harness. You had to move, stretch or hang several wiring harness's out the way for your engine install which would include the fuel injection and ignition wiring harness's. That movement of those harness's could have caused the problem your are experiencing now due to an old, broken or fragile wire in the wiring harness.

I suggest you thoroughly/carefully inspect visually and with a multi-meter test all the wires in your ignition wiring harness and fuel injection harness to see if you might have the same issue that caused the same problem I experienced years ago.

Co_94_PU

iTrader: (-1)

That really isn't how wire insulation works. Having exposed wire in a system is never a good thing, more so when it is an ignition trigger line.

..

Above i left out a bit..running a compression test while the engine is warm. This points to things like valve leaks from over tight valve adjustments (compression numbers that never want to reach the spec), inadequate air flow from loose valve adjustments (compression figures that take longer than average to reach spec).

Suck, squish, bang, blow all at the right time and volume are what make engines run.

...
Saying "yeah I did all that, what am I missing" without giving specific values and/or the test results just doesn't work for anyone does it?

vintageracer

That may be true about how and why insulation is on wires HOWEVER that still not change the reality of V= I x R and HEAT to copper a wire can cause a lot or R!

Co_94_PU

iTrader: (-1)

0.00085 to 0.0015
20° to 170°

Let's call it double the resistance, which ups the current draw about 50%.. It's a CMOS circuit so voltage range is 3.5-5volts.. So if you're following along and doing the math your jaw just hit the floor as the current went from ~5000A to 7500A. The very important part that you might be overlooking is the current limiting resistor, which is going to have a huge value compared to the wire.

A much more likely culprit than heat in the wire is the surface corrosion of having exposed copper, combine this with the twist unfurling, a few broken strands here and there. This of course ignores the odds of a short circuit. Now we've probably dropped the volt and a half keeping the ignitor from charging the coil, or discharging it (depending on the design)


These are certified designs intended to work in the automotive temperature range of 175°C.

I am know to be abit hard on the cost cutting engineering step, but even they don't screw up things that bad.

chuckross1957

The next time this happens, try pulling your fuel pump relay. Then try starting the engine with the relay removed. If you try to start it a few times and then it starts and runs for a few seconds, you have too much fuel similar to being flooded on a carbed engine. If this turns out to be the issue, you might want to install an on/off switch for the fuel pump in the cab as a work around for the problem. You can use the switch as an anti theft device also.

Oberon

Figure anything out? My v6 does the same thing.

peterbilt385

will do thanks, however I don't think this is the issue. I can spray gas in the intake and she will fire.

peterbilt385

temp sensors are all new. I will check wiring again and try to set up a fuel pressure check as well. thanks

peterbilt385

temp sensors are new.