Hard/long start issue 96 roadmaster wagon

My daughter's 96 roadmaster wagon has developed an issue when she goes to start it. Turn the key and the starter cranks like it is supposed too for about 5-10 sec and nothing. Lets off on the key and tries again and on the second try 7 out of 10 times the car will fire right up as if nothing was wrong with it. Sometimes it goes to three times and again fires right up like nothing is wrong. the car runs and drives like it should except for this issue. Here is what I have done to try and find/fix this problem. Checked fuel pressure and it checked out ok and in the range 45 PSI. replaced the fuel filter, ignition module on cylinder head, looked for kinks in fuel line. I am looking for some help here I have the car at home for two months then she needs to take it back to school 1200 miles away. So I would like this problem fixed before she goes back. The mechanics in here town told her to drive it and not worry about it but I know its not right. So any help please would be greatly appreciated. Thanks Dan

 

I'd take a good look at the ignition system, aren't these the 5.7s that had the distributor behind the water pump? I seem to remember that they were, the shaft seal would leak and contaminate the cap & rotor and crack in the reluctor would affect the Hall effects switch inside. Replacements are pretty cheap, I'd also look at the crank sensor, any deterioration in the wiring to it? If it's not fuel it must be spark so that's where I'd go next.

 

Actually, it may be a lot more simple than that. GM engines are wired with an oil pressure switch that, if the fuel pump relay fails to work, the switch closes during cranking when the oil pressure goes above 4 PSI. To begin, pull the fuel pump relay out and disconnect it. Look for burned pins, usually caused by loose female terminals in the connector. If there are any, the relay and connector pigtail will require replacement. If not, using a small pick, carefully snug up the terminals so that they make a tight connection. Reconnect it. Then, while holding the relay, have someone turn the key on. The relay should cycle for two seconds, which your hand will feel if the relay works. Hook up a 12 volt test light if the relay clicks on. The pump power wire should have power when the key is turned on. If not, replace the relay.

 

You're on the right track with the fuel pump relay. GM used two parallel paths to operate the fuel pump on these cars. The ECU closes the relay for two seconds when you first turn the key to START to pressurize the system. Once the engine starts and oil pressure builds, the oil pressure switch closes, bypassing the relay and powering the pump. What is likely happening is that the relay has gone bad or is otherwise not closing, so you have to crank the motor until oil pressure builds.

An easy test is to simply remove the gas cap and listen at the tank inlet while someone turns the key to RUN without starting the car. You should hear the pump run for a couple of seconds. If not, the relay or circuit is the problem. A fuel pressure gauge on the test port is an even better way to test - look for a pressure rise when you first turn the key.

 

Hopefully it's not the ECU, a friend of mine's car won't turn the fuel pump relay on from the ECU port for some reason (had to bypass it to get it on).

 

Thanks guys you CAN hear the pump run for a few seconds before start up. So I know the pump is activated at the start.

 

If it cranks for a while and pressurizes the oil pressure switch the pump will run for a few seconds just before starting. The test is if it runs for 2 seconds when you initially turn the key to the on position. You test after the ignition is turned off for ten seconds are the instructions in the '92 manual.

 

If the pump is coming on before the engine turns over, then put a pressure gauge on the test port and see if pressure is building. If not, the regulator may be bad or sticking.

 

A lazy injector can also do that, let too much fuel and pressure out, making buildup difficult. And yeah, there's more than one way to skin a cat.

I found Dan had opened a thread for this problem over on Ranchero.us; when I saw it and couldn't find a post by me I thought I was going crazy!

 

Thanks guys for your replies. The fuel pump on this best has over 240K on it probably would not hurt to replace it. While running it has about 40 psi. At first start I get 25 then I turn the key off and on again and it will go to 40. that is when it will start.

 

Sounds like you've found the problem. Fuel pressure on these should be 40-45psi to run properly.

 

With that mileage, you might still want to pull the pump relay and 'snug up' the female terminals in the connector. It'll go a long way in preventive maintenance.

 

Your fuel pressure regulator is bad. Those starting issues are the exact same ones I had on mine. The diaphragm inside your regulator is leaking. I'm 99.9% sure this is your problem.

It's not expensive, but is a little hard to reach as it mounts to the very rear of the intake, between the intake and the firewall. Part is around $100 at most chain parts stores. Again VERY COMMON issue on LT1 engine. I know from experience, having done this on my '96 Roadmaster wagon last year. Symptoms you described were just the way my car was acting.

Pic here for location: http://shbox.com/1/fp_reg.jpg

 

Just be glad it's not a Camaro/Firebird. These are impossible to get at one those...where the motor sits under the windshield. Not too bad on a big B-Body!

 

You DO want to replace this regulator soon, as it can cause a flooding issue at startup. If it's been doing this a while, it would be a good idea to change your engine oil and filter at the same time, as your oil may be contaminated with fuel...which does not make older engine/piston rings happy.

And avoid those other mechanics that told you not to worry about it. You were correct, the issue was not "right".

Good Luck!

-Mike