I own a 1994 Buick LeSabre. I bought the car new and have always maintained it very well. The car currently has 96K. Last year during winter, I changed the original fuel filter. Immediately afterwards, my car started exhibiting a hard to start condition in temperatures below ~40 degrees. Trying to correct the problem I repalced, the Idle Air Control Motor, MAF, Cooant Temperature Sensor, plugs and wires. I also tore apart the engine cleaning the throttle body and repalcing the Upper Intake Plenum and the Lower Intake gasket (which was in very bad shape). I put everything back together and the car still exhibts the same hard to condition when the temp is below 40 degrees. I then checked the fuel pressure and with the key in the "ON" position and found the PSI to be 41; however, once the relay clicks it drops down to 36 psi. I also checked the fuel volume and it is 47 to 48 seconds for one quart. Is the fuel pressure and volume acceptable? If not, could my fuel pump be the problem? Any help is appreciated.

You done a lot of good things to your Buick. From here, I would focus on the fuel pump, Crankshaft Position Sensor, Camshaft Position Sensor, and Ignition Control Module. Check in a Haynes Manual what the fuel pressure should be. I suspect it should be around 45 psi.

Haynes states that the fuel pressure should be anywhere from 41 to 47 PSI. As I mentioned, with the key in the "ON" position, the PSI is 41; however, 2-3 seconds later the relay clicks and the PSI drops down to 36. I have researched this problem and a few sites say that my 36 psi is acceptable, but other sites have stated that the PSI should not drop below the MFG rating on 41 to 47. Which is correct? Also, is the fuel volume of 47 to 48 seconds for one quart acceptable?

Check what pressure the Fuel Pressure Regulator should maintain--that may be key. Here's a typical operation.

Fuel Pressure Regulator Test

The fuel pressure regulator maintains a constant fuel pressure to the fuel injectors. When the difference between the fuel pressure and manifold pressure exceeds 43 psi, the diaphragm is pushed upward, and the excess fuel is fed back into the fuel tank through the return line.

Test:

1. Attach fuel pressure gauge to service port of fuel filter. Pressure should be 40-47 psi, with fuel pressure regulator vacuum hose disconnected and pinched.

2. Reconnect vacuum hose to fuel pressure regulator.

3. Check that fuel pressure rises when vacuum hose from fuel pressure regulator is disconnected again. If fuel pressure did not rise, replace fuel pressure regulator.

I suspect the flow is acceptable but the pressure appears a little low.

Other Thoughts:

Were the spark plugs made by ACDelco?

Have you removed and placed the battery on a charger, cleaned battery terminals, and cleaned cable connections? Most auto parts stores will charge batteries for free. Be sure to check the electrolyte levels, adding distilled water as needed. Temperature drops can be telling on batteries.

I just checked the fuel pressure. I connected my gauge to the fuel rail and then started the car (the car started easily since it was still warm). Fuel pressure was 36psi after it started. I then disconneted and pinched the vacuum hose to the fuel pressure regulator and the pressure rose to 45 psi. I then reconnected this FPR vacuum line and the fuel pressure dropped back down to 36 psi. I think my FPR is good (also, it does not leak).

Additionally, I replaced the spark plugs a few days ago with AC Delco brand (exact match to what the car originally came with when new). The battery too is brand new (Diehard with plenty of CCA). It has side posts and the positive and negative connections and they are very solid with no corrosion. In the morning when the temperature outside if below 40 degrees, I sometimes have so much trouble starting the car that I end up draining this new battery and have to put it on my charger for a few hours. I don't think the plugs, battery or the battery cables are causing this issue. What I am thinking is that I could be one of the following:

1) My spark from the coil pack could be weak
2) Fuel volume from the fuel pump is low
3) The fuel pump's check value is bad

What do you think?

Greater than 90% of all crank but won't start situations are electrical related, not fuel. Because of the age of the car, I wouldn't be surprised if the Ignition Control Module (ICM) is intermittently failing. They are quirky and problematic components, responsible for more crank but won't start (and sudden death) situations than any other part. This is why I recommend changing them every 120,000 miles or 10 years, whichever comes first. I think your fuel system is now fine--maybe a tad low. Plug your coil packs into a new ICM and I bet your problem will be solved!

Thanks TxGreaseMonkey for all your help. I will pick up an Ignition Control Module tomorrow and hope for the best. Thanks again.

Buicks are good, reliable cars. My son drives one in L.A. and I have been impressed with how well it has held up under brutal conditions.

Shop for price and warranty.

Did you ever check for codes?

Here's what Bosch says concerning fuel pump flow rates:

Modern EFI fuel systems circulate as much as 200 litres per hour (~ 3 litres/min) of fuel at pressures between 2.5 – 3.5 bar (250 – 350 kpa).

When the temperature drops below 40 degrees F. try turning the ignition switch to RUN, until the fuel pump stops running; then, turn the key OFF. Repeat this procedure several more times. This should fully pressurize the fuel rail. Finally, turn the ignition switch to START. Fuel may be draining back during the night.

Based on what Bosch says, and your suspicion, your fuel pump may need replacing. I've seen very few fuel pumps that are really bad, even though many mechanics are quick to replace them. Replace it as a last resort.

Well, I still have this same problem which is the car will not stary when the temperature drops below ~ 40 degrees. The colder it gets outside, the more difficult it is to start. Since my last post, I decided to replace the fuel pump, the gas tank and sending unit (tank was rusted and the plastic inlet and outlet lines were froze onto the sending unit) so I repalced everything. However, once I reinstalled everything I still had the same problem. I then picked up a new ICM and that too did nothing to correct the problem. So to recap:

Vehicle: 1994 LeSabre with 125K. Owned since new.

Location: Chicago

Problem: My car has started to exhibit a "hard to start condition when cold." When the Ambent temp. is ~40 degrees or < the car becomes increasingly difficult to start. The colder it gets, the harder it is to start. However, if it warms up to ~40, it starts fine.

Parts Already Replaced: Coolant Temp. Sensor, IAC, MAF, EGR, ICM, fuel pump, fuel filter, sending unit, gas tank, starter & battery. I also tested the coil pack; however, the primary and secondary resistance on all three coils is within spec. Furthermore, I dug into the engine replacing the Plenum (and it's gasket), cleaned the throttle body, the lower intake manifold & replaced the LIM gaskets. Also checked the fuel pressure regulator and it is NOT faulty.

Check Engine Light Codes: NONE

Any help is greatly appreciated!

Additional Thoughts:

. Check/replace the Crankshaft Position Sensor.

. Check/replace the Camshaft Position Sensor.