I have a question about why my truck won't start unless I spray starting fluid into the throttle body. After it starts, it will keep running. If I turn it off it will start right back up, but if I leave it sit for 10 or 15 minutes, I have to spray fluid again to start. It is a 1990 ford 5.0. I've replaced spark plugs, plug wires, coil, ignition module, distributor cap, rotor, tps, air intake temp sensor, fuel pump, pressure regulator. The only other thing I can think of replacing is the maf sensor or the fuel injectors. It is burning a lot of fuel. I sure would appreciate it if someone would offer some suggestions on what could be causing this problem.

 

How many miles are on the engine? Do a compression test.

 

The engine was rebuilt about 3 years ago. Probably has around 30,000 miles since. The problem was not a gradual deterioration in performance, but began suddenly one day. Up until then it started right up without starting fluid and had good gas mileage.

 

The symptoms are like the fuel isn't being enriched when cold like the computer is in closed loop mode instead of open. I assume the inlet air temp sensor you replaced is part of the circuit that tells the computer to go into closed loop mode. Have you checked for vacuum leaks? I'm just wild guessing here. Maybe one of the real mechanic members will chime in.

 

Thank you for your reply. All of the vacuum lines look good ( not dried out,no cracks, or bad connections ). I tried listening for any leaks, but couldn't hear anything over the fan noise. I just did a leak down test on the fuel pressure. The KOEO test read 42 lbs of pressure but when I turned the key off, the pressure dropped to zero within a few minutes. I then repeated the same test, but this time I pinched off the fuel return line right after turning the key off and the pressure held. I believe this would indicate leaking fuel injectors. I guess I have no choice but to replace the injectors and hope that solves the starting issue. If that doesn't work, it's "goodby truck".

 

Wouldn't that indicate good injectors if the pressure held with the return line pinched off? There is an answer to this and it may not be that expensive to repair. I'd be so curious, I'd have to find out what it is. Perhaps it's time to consult a mechanic?