Fuel pump and FPR recommendations?
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HT4100 4.1, 4.5, 4.9 Discussion, Fuel pump and FPR recommendations? in Cadillac Engine Technical Discussion; I've been having hard hot start issues more and more frequently so I decided it's time to get a pressure ...
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    Fuel pump and FPR recommendations?

    I've been having hard hot start issues more and more frequently so I decided it's time to get a pressure gauge and start poking around in there... I've determined that it's either the FPR or the fuel pump check ball but I cant go much further until I get a test gauge.

    There's no fuel at the FPR nipple, and the injectors are fairly new but the system does not hold pressure overnight.

    Anyways, I was wondering what are the most reliable brands for fuel pumps and FPR's?

    According to my wallet, AC Delco is out of the question so it's looking like Bosch, Airtex, BWD, CarDone, etc etc

    What do you guys think?

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    Re: Fuel pump and FPR recommendations?

    I can't speak for fuel pumps. Just an FWI, I have never heard of the fuel pumps check valve failing, though it's possible. Almost every time I've had the fuel system bleed pressure, it was either the FPR or injectors...

    Anyway, for the fpr, I've used BWD on all of my 4.X's. BWD's unit is brass, and therefore fairly resistant to corrosion. Many other brands don't offer this. I replaced the fpr on my '95 twice due to a failed, cheap unit from Autozone but I can't remember the brand. It was poorly made, corroded within weeks, and leaked 3 years later. All of my BWD fpr's are still in service and work great. I highly recommend if available.

    You can see the unit here on my '95 4.9. It was changed quite a while ago and still looks and works like brand new...

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    Re: Fuel pump and FPR recommendations?

    Thanks! Thats the one that Advance has for 49.99. I've about had it with autozone parts... they just dont last like OEM. It's too bad that Delco parts are outrageously priced. A delco 7-pin ignition module is 62.99 vs 21.99 for the BWD part.

    I'm leaning towards it being the fpr... I'm going to cap off the return line and then pressurize the system and see if it bleeds down. If it doesn't, then its the FPR. I doubt its the injectors since I had the problem before I swapped them to Bosch III's.

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    Re: Fuel pump and FPR recommendations?

    Btw, besides hard hot starts, what driveability issues did you have when the units failed on your 95?

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    Re: Fuel pump and FPR recommendations?

    It could be your starter. Check the fuel pressure before playing with pump.

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    Re: Fuel pump and FPR recommendations?

    Quote Originally Posted by Sevillian273 View Post
    Btw, besides hard hot starts, what driveability issues did you have when the units failed on your 95?
    Hot starts are mainly the concern due to an overly rich mixture from teh extra fuel in the intake manifold. Depending on the size of the leak, you can also experience a rough idle and poor mpg's. I experienced these in both the '90 and the '95 4.5 and 4.9

    If you want to eliminate the check valve in teh fuel pump, I would suggest cycling the ignition on and off a few times to prime the system. If you still experience the same symptoms, I would look elsewhere. However, if the car starts right up like nothing happened, you might be on the right track.

    Be sure your pressure gauge itself doesn't leak and is fairly accurate...

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    Re: Fuel pump and FPR recommendations?

    The idle is just a tad bumpy at times, mpg seems ok(22+), but the pedal is very touchy from a stop... Theres very slight delay and then suddenly the car wants to jump out of the hole and spin the tires - presumably after eliminating the extra fuel from the leaking FPR.... Like going from rich(bogging) to normal (ZOOM!) in a split second. I'll know more later when I get a gauge.

    Its definitely not the starter. The cranking system is in perfect order. Like I said, the main indicator here is that the system does not not hold pressure overnight.

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    Re: Fuel pump and FPR recommendations?

    Quote Originally Posted by Sevillian273 View Post
    The idle is just a tad bumpy at times, mpg seems ok(22+), but the pedal is very touchy from a stop... Theres very slight delay and then suddenly the car wants to jump out of the hole and spin the tires - presumably after eliminating the extra fuel from the leaking FPR.... Like going from rich(bogging) to normal (ZOOM!) in a split second. I'll know more later when I get a gauge.

    Its definitely not the starter. The cranking system is in perfect order. Like I said, the main indicator here is that the system does not not hold pressure overnight.
    That's exactly what my '90 Eldo was doing with the fuel system leaking into the intake. Along with the engine hard starting and sometimes killing while putting in gear on a hot start.

    However, it could be a host of other things as well, including running too lean. My '90 Eldo also started giving the "jumpy"/delay/stumble feeling you are talking about when an intake manifold gasket leak started. The problem felt like a bad accelerator pump on a carb'd engine. The mixture would be too lean to run correctly for the split second the throttle was opened suddenly. However, it would run fine outside of that split second.

    I'd have the car put on a scope and have it diagnosed before throwing parts at it.

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    Re: Fuel pump and FPR recommendations?

    The rest of the engine's components are in good working order and most of the ignition system is less than 10K miles old. Everything is in spec save for the fuel system since it cant hold pressure very long... TPS, ISC, EGR, EVAP - all in perfect working order. The injectors are Bosch III's just recently installed, oxy sensors less than 10K, all filters less than 10k, etc etc... Everything has had my attention except the FPR and fuel pump. I'm going to follow the FSM in diagnosing it. At this point, everything hinges on what the fuel pressure gauge and the 'return line cap test' reveals. I've had the hard hot start issue since I bought the car almost 2 years ago. The fuel pump runs and has always had no problem keeping up with the engine's demands so I'm heavily leaning towards an internally leaking FPR. I'm just waiting on a paycheck so I can go ahead and get the gauge and make some more progress on this.

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    Re: Fuel pump and FPR recommendations?

    You don't need a gauge or any tool at all to check the FPR.

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    Re: Fuel pump and FPR recommendations?

    Quote Originally Posted by Ranger View Post
    You don't need a gauge or any tool at all to check the FPR.
    He would to diagnose an INTERNAL fpr leak like he suspects, which is probably a great place to start. Somehow, he will need to know if the fpr is passing too much or not enough fuel to the return line.

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    Re: Fuel pump and FPR recommendations?

    Quote Originally Posted by Ranger View Post
    You don't need a gauge or any tool at all to check the FPR.
    No fuel at the nipple.... At least not at idle... Like drew said, I think its leaking into the return, that's why I'm going to cap it and turn on the key to check. Looks like a 3/8 brass plug is what I need..

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    Re: Fuel pump and FPR recommendations?

    There is a diaphragm in the FPR that separates the fuel side from the vacuum side. If it leaks, fuel is present at the nipple. If there is no fuel, it's good. Simple as that. An internal leak will leak through the nipple, externally.

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    Re: Fuel pump and FPR recommendations?

    Yup, I've been wrong about how the FPR works this whole time. I always thought it worked by dumping excess pressure back into the tank...

    Anyways, I finally got a test gauge today and here are the results:

    --Engine hot, extended crank condition not present--

    Key on: 40psi

    At 600 rpm: 34psi

    Varied rpm(idle - 2000): 31-35psi

    With fpr hose removed at idle: 45psi

    FSM spec is "34-38psi and varies with engine load"

    After an hour I did not observe any bleed-down but in the past there has been slim to no psi remaining overnight...

    Results so far are pointing to a weakening fuel pump... I'd like to test pressure when the extended crank issue is present but unfortunately the chance of that happening in my driveway is slim to none.

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    Re: Fuel pump and FPR recommendations?

    I always thought it worked by dumping excess pressure back into the tank...
    It does. At idle (low fuel demand) the engine vacuum is high and pulls the FPR diaphragm open, thus opening the valve to the return line. At WOT, engine vacuum drops to near zero and leaves the spring loaded valve with no vaccum and the valve closed, thus delivering full fuel pressure to the injectors.

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