Fuel Pump Fails to Deliver the Needed Power
Question: I have a 1984 Toyota Camry with 70,000 miles on it that has developed a very perplexing problem over the last couple of years. On many occasions (but not always) the engine loses power or stalls as I climb virtually any kind of a hill. The engine does not downshift automatically as the speed drops unless I manually put it into a lower gear. I have had the engine tuned and the fuel pressure and ignition checked. Since it is difficult for a mechanic to duplicate the condition that causes the problem, I’m at a loss for finding the cause. Other Camry owners tell me they have the same problem. Do you have any advice?
--L.J.F.
Answer: There are two distinct problems with the Camry that can cause stalling on hills and the solution is relatively straight forward, though not exactly inexpensive.
The 1984 Camry has an electric fuel pump made by the Japanese supplier Nippon Denso that suffers a loss of volume under high temperatures and high demand. When you climb a hill, especially at freeway speeds, the engine needs to consume a maximum amount of fuel. The Nippon Denso pump fails in its ability to deliver fuel, even though it can maintain sufficient pressure.
Mechanics will often test a fuel pump pressure but skip testing whether it can deliver adequate volume. The volumetric test is more difficult to perform than the pressure test. If the pump can not deliver adequate fuel, the engine starves, power is lost and, in the worst case, the car stalls.
Toyota recognized this problem a long time ago and established a policy of repairing such fuel pumps under a program known within the company as “customer satisfaction.” Some people would call that a secret warranty program.
The free fixes were usually provided on cars up to 36 months old or with less than 36,000 miles on the odometer. If you can show, however, that you had reported this problem a long time ago when you car still qualified for the free repair, you very possibly can get Toyota to repair the pump for free. You undoubtedly will have to make a lot of noise complaining and you almost certainly will have to haggle with a Toyota factory representative.
The second possible problem is that your engine has developed carbon deposits on its exhaust valve. Under high engine temperature conditions, which are created on hill climbs, the deposits prevent the valve from fully closing. If the valve can not close, then some of the explosive fuel-air mixture will seep out on the engine’s power stroke, robbing the engine of power.
To fix this condition, the head must sometimes be removed and the carbon deposits removed. You might, however, try a fuel additive that claims to reduce carbon deposits in the engine.
Q: I have a 1990 Honda Accord, which makes a terrible cracking or popping noise every morning when the engine is heating up. Once it heats up, it stops. My dealer insists this normal, but I find it a nuisance. Is there really a problem behind this noise.
--M.T.
A: In all probability it is simply the catalytic converter heating and the metal expanding. The converter runs at temperatures up to 1,200 degree, so when it warms up from under 100 degrees the metal undergoes a substantial amount of thermal expansion.
It is not uncommon for newer cars to crackle or pop, both when they are warming up and cooling down. It is annoying to you probably because you simply don’t understand it.
