454 XLi Wonbt Start

"After refurbishing the heads,

"After refurbishing the heads, cleaning out the filter housings and replacing the distributor cap and rotor this RH rotation engine started & ran fine for 3 hours. Then began to surge(at first 200 RPM then wildly) and stopped. won't start since.

Cleaned the TBI fuel injectors (they were pretty gummy according to the injector cleaner). Timing is set per spec. Fuel is relatively fresh stabilized (sta-bil)no ethanol (tested for alcohol). Spray cone looks OK. Checked voltage at the fuel pump, seemed OK, replaced the fuel pump.

Pump runs for 4+/- sec when key on. Fuel pressure does not build to 20 PSI until I stop cranking - then it goes to 20 and drops to 0.

I am thinking fuel pressure regulator in the TBI, oil pressure switch, finding a mechanic with the code reader, or have I completely missed something simple? The other engine starts and runs OK but probably needs to have the injectors cleaned as well."

you say the pump runs for ~ 4

you say the pump runs for ~ 4 seconds when the key is turned ON - what does the fuel pressure gauge do during this time?

The other "working" engine can be used as a reference.

Good point. I will check on t

Good point. I will check on that engine. The gauge slowly rises to maybe 10 PSI then drops back to 0 when the pump stops.

"I don't have an XLi manua

"I don't have an XLi manual but 10psi seems way to low and 20 psi about marginal. If the pump runs, you can rule out the oil pressure switch (1/2 anyhow) leaving the pump or the regulator.

Most of the TBI setups I've seen don't monitor the fuel pressure so you may not find a code set."

20 PSI is the spec. for delive

20 PSI is the spec. for delivered pressure (at the port on the delivery side). Working pressure after the regulator is supposed to be 13 PSI. but there doesn't appear to be a way to measure that.

What do you think about jumping 12 v directly from the battery to the pump? The return line may eliminate an excessive pressure build up.

I will check the other engine fuel pressure tonight when I get a chance.

"The pressure returning to 0 w

"The pressure returning to 0 when the pump is off seems ok as long as it is a gradual drop and not sudden.

I'm thinking filter restriction or pressure regulator. I'd start with a filter swap if not done recently (& make sure the shut off valve gets opened fully). If the regulator is vacuum controlled, you can pinch the return line to see if the pressure builds with that "restriction". If the pinch trick shows improvement, you could swap regulators to see if the issue follows the part."

"The filters are all new, the

"The filters are all new, the housings cleaned and the valves are wide open. As far as I can tell there are no fuel line restrictions.

I will check first the other engine fuel pressure and pump operation. Then take the regulator assembly apart. It is part of the TBI and although Rochester says it's not field serviceable, the parts were included in the gasket kit. I misspoke, the working pressure is specified at 10-12 PSI.

Thanks for your insight. I'll post what happens."

"Transferred the pressure gaug

"Transferred the pressure gauge to the other engine. Did the 5 sec/10 sec priming process once or twice. Fuel pump ran pressure moved smartly to 20 PSI then dropped back when the pump stopped. Tried starting, started right up and pressure dropped to between 15 & 20 PSI.

Went back to the problem engine. Did the 5 sec/10 sec procedure. First 5 sec, pressure ran up to about 20 PSI then dropped back. 2nd 5 sec on - NO pump run. Tried 2 more times with nothing. Tried to start and got some pump run & pressure but it would not continue to run. I'm leaning toward something in the wiring between the starter (that should over-ride the oil pressure switch) and/or the oil pressure switch or wiring."

"So what you have is intermitt

"So what you have is intermittent fuel pump operation.

You could have the SPDT oil pressure switch controlling the fuel pump (no ECU control). These have three terminals with the common terminal going to the pump. Typically, the STARTER circuit feeds +12V to the pump thru one terminal and the other is feed by the ignition circuit. You can bypass it to test it but I wouldn't do it for anything beyond that. you could also feed the pump via a fused jumper lead."

"Mystery solved. An hour with

"Mystery solved. An hour with a Crusader mechanic and a new Ignition Relay later, the engine runs perfectly. The relay may have replaced the SPDT switch in the oil pressure switch since there was only 1 wire going to that switch instead of 3 like the older models."