motor starts better in colder weather then hotter weather

i have recently rebuilt my 351w. the same motor that has given me all those other problems. but now that the weather is warming up the truck some of the time is having problems starting. ill put it this way when the weather was cold the truck would start right up no problem. it evened seemed that the colder the better. But now the weather is warming into the 80's and some of the times when i go to start my truck, it will take a while to start. i have to hold the key on the "on" position then let go and do it again. You can hear the starter working great and the battery is new, the truck sounds like its not getting any fuel to start. But then other times the truck will start right up no problem. Any ideas or comments. i drive the truck daily as well.

If it is carbureted then it starts easier with cold weather because your choke is set and is not setting now. If you pump the gas once the choke should engage and then start right up Assuming it is carbureted of course.

It's not carbureted. It is fuel injection

yo BB,

Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19

http://broncozone.com/topic/14269-code-reader/?pid=74587&mode=threaded

A helper is good to assist in reading Codes; best is to take a cell fone vid and replay it.

Some basics;

Visual Check

Battery is fully charged & connectors and grounds are clean

Inspect the air cleaner and inlet ducting.

Check all engine AND HVAC (under hood & in /under dash) Vacuum hoses for damage, leaks, cracks, blockage, proper routing, etc.

Check headlights

Check EEC system wiring harness for proper connections, bent or broken pins, corrosion, loose wires, proper routing, etc.

Check the Powertrain Control Module (PCM), sensors and actuators for physical damage; can use these two diagrams to locate ACT, TPS, EVP above EGR), Ignition Control Module (ICM) on distributor mounted years (Ford re-located the ICM from Distr side to driver side hood hinge area on inner fender liner in 92-96); to MAP;

http://www.revbase.com/BBBMotor/Wd/DownloadPdf?id=14698

http://www.diesel-dave.com/vehic/manual/stj/stj31b21.htm

Sensor Locations Diagram ECT, IAT and Water Temperature Gauge Sender

Assuming no fuel leaks (also check near fuel injectors beside usual suspect areas;

seems similar to what I have seen in other 90-96 Broncos and Ford trucks w/single tank.

The in-tank fuel pump assembly has a discharge check valve (to maintain system pressure during shutdowns and to minimize starting problems), an inlet screen for protection and fuel return provision.

The Supply Check Valve, which is normally closed, opens when the outlet pressure from the energized pump exceeds the opposing check valve spring force. When the pump is de-energized (i.e., engine is shut off), the supply check valve closes to maintain pump prime and fuel supply line pressure.

Note: Maximum fuel pressure is obtainable at WOT or the vacuum hose removed from the fuel pressure regulator.

If fuel lines/systems have been drained or evacuated, it may take up to 15 seconds to obtain the pressure specified.

I believe the PUMP's check valve is Stuck in open (full flow) state and allowing fuel to return to tank, thus reducing fuel pressure while engine is off.

I have a slightly similar issue when first starting in morning or after long shut-down; engine will crank over normally, but not run or run rough at low RPMs until it runs or shuts down. If I hear it stumbling, I shut it off, then turn key to start; it will fire up immediately.

I may try a Ford type fuel cleaner soon.

This is by Ryan M; "After attaching the fuel pressure tester, run the fuel pump for 10 seconds. Check that the pressure is within specs, and it doesn’t leak down more than 5PSI within 60 seconds after pump shutdown."

FP;

KOER 30-35 PSI

KOEO 35-45 PSI

Note: Maximum fuel pressure is obtainable at WOT or the vacuum hose removed from the fuel pressure regulator.

Hey BBU,

The first thing to do is to see if it is getting spark and fuel. When it "fussy" starting, have a friend crank it and use a test light between the + and - terminals of the coil.

If you have the test light flash it is getting a spark signal, and all the primary side of the ignition is ok.

Next try spraying some carb cleaner in the intake hose. (the big rubber conduit between the air box and the throt. body.) You can get a can with the little straw and slip the straw in the hose after loosening the clamp. If the engine starts with the extra shot of carb cleaner, then the problem is fuel.

A coolant temp sensor could be the problem and not send a code. ACTS could be an issue too. But first we need to know if it's a fuel or ign. issue.