Concorde Fuel pressure

More than likely, one of two things is happening: (1) One or more injectors is leaky - when the car sits with engine off, for a few hours, the fuel rail empties out into the cylinder or cylinders with the leaky injectors. When you go to start it back up, the fuel pump has to first re-fill the fuel rail before it can supply and pressurize the injectors. (2) Check valve back at fuel pump is leaky - fuel lines empty out with similar results - pump has to refill system before cylinders see fuel from injectors.

I don't know about 1st gen LH's, but on 2nd gens, the way to prove that either (1) or (2) is happening is to turn key to run (not start) for a couple of seconds, then to off, then again to run for a couple of seconds, then to off, then to start - if it starts on the first try after doing that, then either (1) or (2) is the problem. The reason is that the fuel pump shuts off after a second or so if it does not detect engine start. By cycling the key a few times, you let the pump run for several of those second or so bursts - enough run time to refill the rail. If you try to start without cycling the key, the single burst of pump run time is not enough.

Pressure regulator for 2nd gens is in the fuel tank (part of sender/pump assembly) - 1st gens are probably like that too - but not sure. But that is probably not the problem - see (1) and (2) above.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

The upper plenum has to come off (I'm assuming a 3.5L engine). Its not a big job, really. A quick check is to pull the vacuum line off the fuel pressure regulator and see if fuel comes out, indicating a leaky diaphragm. Been there, done that- it caused fuel pressure leak-down over a few hours, followed by longer than normal cranking on the next restart to rebuild the fuel pressure and clear the leaked of fuel out of the vacuum lines.

Nope, that's one of the things they cheaped out on the second gens. First gens have a full recirculation type fuel loop. The pressure regulator is in the fuel rail, and fuel "bled off" by the regulator returns to the tank, keeping cool fuel at the injectors at all times. I think the purported reason (rather than just admitting "we're cheap" ;-) for the change was that a recirculation system causes the fuel in the tank to become a few degrees warmer over time, and thus increases evaporative emissions. But the cool fuel at the injectors is sure nice for performance and consistency.

More then likely the fuel pump check valve is bad causing the fuel to drain back to the tank as Bill said. The injector(s) could also cause this problem but if that were the case you would have a hard time starting this vehicle after a hot soak.

Glenn Beasley Chrysler Tech

OK - I stand corrected. Thanks.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

The regulator is under the intake on this model. If the regulator is bad there would still be fuel from the pump to the fuel rail The pump still has a check valve built into it to prevent fuel from draining back to the tank.

As far as the fuel loop goes you have it backwards or Im just reading it wrong. when the fuel regulator was at the intake it caused the fuel in the tank to heat up, causing higher emissions. By having the fuel pressure regulator on the pump in the tank, it keeps the fuel at a cooler temperature. This is done by not having the fuel heated up by the exhaust and under hood temperature and then going back to the tank

Glenn Beasley Chrysler Tech

Right (allegedly).

The fuel in the TANK stays cooler without a loop, but the fuel AT THE INJECTORS is much hotter, because intsead of continuously circulating it just flows slowly through the rail warming up to the temperature of the cylinder head or injector that its flowing into. That's the whole reason that the carbureted Hemi and 440 Magnum cars of the 60s had a similar fuel loop that pumped excess fuel from the filter back to the tank, so that the fuel headed to the carb would be as cool as possible to prevent vapor lock. Its not as big a deal on high pressure fuel injection, but keeping the fuel cooler is always a little better for engine performance and consistent mixture control.

Glenn - I'm thinking that the fuel mass in the engine compartment environment (in the lines and fuel rail) is a *lot* less than the volume in the tank - therefore, with a given number of calories absorbed by the lines and rail, it's temperature rise without the full loop circulation will be a *lot* higher than the rise in the whole tank (from the heated fuel returning to the tank), plus heat dumped over that huge volume back at the tank will also be dissipated at a moderate enough rate into the ambient due to the large surface area if the tank acting as a radiator - the net result of the full loop circulation will be lower temperature at the point of injection into the plenum.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

Possessive: "ITS" Contractive form of the third person "to be": "IT'S"

GOTCHA!

Putney's right here. I have an exact same, but much larger, model I dealt with when retrofitting emergency diesel and gas turbine generator fuel tanks back in the '90s.

Most original installations of these were much like the older FI system....diesel or JP-4 would be pumped into a day tank, the engine would take what it needed from there, and return excess fuel from the pump or rail directly to the fuel tank through a separate return line. Contractors, looking to make a extra bucks on loosely spec'd "design and build" contracts, would replace the tank with a double wall replacement (usually 5K gallons or more) and double wall piping, but only a supply line would be provided, dumping the heated excess from the engine of the generator set(s) into the day tank. The problem was that the diesel would become dangerously hot after hours of operation, the amount varying from model to model and by, of course, capacity.

In the projects of which I was in charge, I demanded that a double walled return line be added to the spec to prevent this. A 10K tank filled with #2 diesel, feeding a 750 KW generator set running at 80% load (Cummins VT-38000/Marathon alternator), with a ground temperature of 19°C, would heat up 4°C after 8 hours operation. However, one "single line" installation, using the same load factor but on a 16V71T Detroit Diesel, would heat the fuel in a 100 gallon day tank up to almost 40°C in half the time period. Detroits run a common loop rail/unit injector system on top of the heads, whereas the Cummins used a PT pump with less exposure of the fuel in the cylinder head area, so there was a little more heat transfer from the Detroit, but the case for the dedicated return line was made, and the company's bid specs were changed to include same.

(Note that I also wasn't stupid enough to use a Detroit Diesel for a generator set engine! What a disaster, but the middle manager "injuneers" at AT&T prevailed on that one. One on them was later allowed to "retire" after rather large kickbacks involving the supplier were uncovered and the IRS started investigating, and AT&T got a little skittish having IRS investigators showing up back in New Jersey.)

I would imagine the same sort of problems with hot fuel due to having the regulator/return in the tank in a gasoline powered car would be similar. The concern of heating of the volatiles in the fuel tank is a non-starter, as well, since the evap system would take care of that at start-up. I think the reason for this change was one that Frank Zappa would full appreciate: "cheapness."

Thats true

therefore, with a given number of calories absorbed by the

Thats true too, but who cares? The higher the fuel pressure the less chances of fuel foaming and all that good stuff. But circulating the fuel back to the tank causes higher fuel temperatures in the tank. thus higher hydrocarbons.

(from the heated

Once again, who cares what the temp is at the injectors???? The ambient temp and coolant temp sensor will adjust for all that. The high pressure fuel pump will eliminate any fuel foaming/vapor lock.

I don't know what all that mumbo jumbo means that you type but since 1998, all fuel systems were designed to be returnless to minimize heat in the tank, which leads to excessive hydrocarbons

Yep. I'm usually pretty good about "it's" and "its". I was running late for work and in too much of a hurry on that one. Check the post time - I have to be out the door no later than 6:41 in order to not be late to work. That's my story and I'm sticking to it.

I still can't keep straight about precede and proceed. If precede is spelled like that, why is proceed spelled like it is - and if it's (ahh

- got it right) proceed, why is it "procedure", yet it's "preceding" and not "preceeding"!?

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

Because, like New Englandese pronunciation, there are NO rules in English...except when there ARE some!

Yes, your usually pretty good about keeping you're "itses" write but you may have been superseded.... ;) (ducking).

Many people don't know this, but Teddy Roosevelt set up a commission to standardize spelling for the nation. I guess for those particular words they may have deferred to common usage spelling in the legal system or something rather than some consistent (and arguably arbitrary) rule.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

Correct. For LH cars (Intrepid, Concorde, LHS), anything prior to '98 is first gen. (there was no LH 1st gen. 300M).

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

If this is the 3.5 engine don't forget there was a recall out to replace the injector o-rings and replace the cracked fuel rail or reinforcing it. Has that been done to your vehicle yet? (assuming 3.5).

Glenn Beasley Chrysler Tech

If this is the 3.5 engine don't forget there was a recall out to replace the injector o-rings and replace the cracked fuel rail or reinforcing it. Has that been done to your vehicle yet? (assuming 3.5).

Glenn Beasley Chrysler Tech

Beauty, eh?