Hello,


Have a strange issue on my 89 C4 coupe that doesn't seem to go away. Everytime I start the car, I have to put the key in and crank the engine 7-8 times before it starts. This happens everytime I start the car and the car always starts afterward. It doesn't matter if the car has just been driven or if its cold or hot outside. There are no check engine lights and the car idles and runs smooth after it starts.



I've replaced the following so far to fix various issues but this one hasn't gone away:
2 Batteries
Fuel Injectors
Spark plugs and wires
Burn Relay
Rotor and Distributor Cap
Air filter
Cleaned MAF
Bypassed VATS



Any Ideas?

 

It seems you've already got to some of the usual suspects for this sort of issue. I'd check the oil pressure sensor for the fuel pump circuit, the fuel pump relay, then the pump, sock, and filter next.

The fuel pump won't run until the pressure sensor sees oil pressure - if that sensor is bad, or failing, the car will crank for a long time before firing up. That sensor enables the fuel pump relay - again, if the relay is failing, it may just be taking some time to actually close. Finally, a gummed up fuel system, or weak pump may be failing to prime the system with enough fuel to start the car.

Additionally, you should observe what happens to fuel pressure while you are cranking - attach a pressure gauge to the schrader valve on the fuel rail, and tape the gauge to your windsheild so you can easily see it while you turn the key. If the pressure drops while you crank, something with the fueling is wrong. If not, your problem may not be fuel related.

 

actually I think if the relay doesn't turn the pump on immediately for 2 sec, then it has to wait until pressure is registered on the oil gauge....
You really have to have a fuel gauge on your windshield to tell if it fires up right away....should hear the relay "click" and the fuel pump go with key on for 2 sec....the experts should weigh in soon to correct me if i'm wrong.....still, the best bet is to have a gauge on your schrader valve...it tells all....

 

It may have changed as the engine evolved, but on my 85 the oil pressure sender is the 'turn on' circuit for the fuel pump. It can prime the system (the 2 sec bzzzzt) without the oil pressure input, but the pump won't come back on until the sensor sees oil pressure. I don't think that the fuel priming would be enough to get the car to do much more than cough, which I why I thought that the pump isn't coming on regardless of the priming.

But, it is valuable info either way - OP, does the fuel pump prime when you turn the key forward? If it doesn't that may explain your hard starting.

 

I have an 85, so you're probably right about that....

 

 

It's hard to tell from inside the car because the buzzing of the power antenna moving is loud compared to any other sounds. Should I stand in a specific spot to hear it?


Also I'll loan the fuel pressure tester from autozone and perform the suggested tests.

 

Fuel pump buzz should be before the antenna moves. Can you turn your antenna of by turning your radio off? Would make checking easier.

 

Thanks, I didn't know turning off the radio would keep the antenna from moving. Now with that off, I can hear about 2 seconds of what sounds like a quiet door creaking. The sound comes on before the antenna normally moves as suggested. Is that what you meant?

I recorded the sound in the video below. Although it very hard to hear, it comes on at the 2-3 second and 11-12 second mark of this video.
https://www.youtube.com/watch?v=4lGg...ature=youtu.be

 

That sounds wrong to me. Should be a more audible 'buzz'. The pump might be on it's way out, or the relay is acting up. Also could be the oil pressure switch that feeds the fuel pump relay. Once you have tested the fuel pressure, we will know more.

If you would like to diagnose the pump prime, you can measure voltage at the fuel sending unit by taking the black rubber piece out. You should get 12 volts for 2 seconds after the key is turned on, and 12 volts while it's cranking.

 

On my '88 the fuel pump relay failure was causing the same symptoms as you describe.

The relay turns on the pump to pressurize the injectors so it can start. The oil pressure switch also enables the fuel pump. So on mine the fuel pressure relay was not turning on the pump for a few seconds to build pressure and it would take enough cranking to get oil pressure so that the pump would come on. I changed the fuel pump relay and everything worked normally again.

However, it sounds like by just turning the key the pump runs before starting the car, so that may not be the cause for your issue.

Good luck.

 

My suspicion is that you are correct based on what everyone wrote on this thread of how the system should work. I'll know more with the pressure tests.

 

Yeah, the prime should happen with key-on, so the pump or relay would be my suspicions.

 

Well if it was the pump itself, wouldn't it not function at all instead of just in the initial start?

 

Most likely. Small chance that the pump has failed in a manner that requires current for time to kick it into motion, then it stays moving. But most likely its the relay. Relays can become slow or sticky over time, so you may not get the pump prime.

 

Guys, The fuel pump relay is the primary source for the fuel pump operation and the oil pressure switch is the secondary source for fuel pump operation. When you turn the key on the ecm will close the fuel pump relay for two seconds to build fuel system pressure. The ecm will also close the relay any time the car is cranking or running so you should hear the fuel pump operating when you turn the key on for the first two seconds or any time the car is cranking. The oil pressure switch closes the fuel pump contacts and powers the fuel pump as a secondary power source. If primary relay has failed you will not hear the pump at key on and it will take some cranking for oil pressure to build up to close the contact and power the fuel pump.

So listen for the fuel pump at key on, if you hear it the relay is fine, if not check the relay for proper operation.

 

Funny thing happened last week I told guys at the Sunday get together in Woodland Hills that I was going to try 87 octane since gas was rising. Next day My car started taking 7-10 seconds to start. I drove a while like that but put in 91 octane and it starts on the first try again. Mabey it was the octane or gas station I don't really kno0w.

 

Measure the fuel pressure via schrader valve on fuel rail before start, while running, and pressure after shutdown. Pressure should be always held at approx. 40 psi.

Possible Root Cause
Fuel pressure check valve in the fuel pump

Symptoms
Long starts
runs fine
good fuel pressure while running
Pressure at zero before start and after engine shutdown

The check valve keeps fuel pressure in the fuel system and prevents it from bleeding back into the tank. Long crank times are necessary if there is zero fuel pressure prior to start because you are re-priming the entire fuel system.

Past Experience
Replaced entire fuel sending unit with pump, and always had long start times since. Purchases a Dorman fuel pressure check valve and installed on high pressure line from pump to fuel rail. Start up was immediate, and pressure at fuel rail was steady at 40 psi even after shutdown. Exchanged sending unit and problem was resolved.

Quality for aftermarket parts is not acceptable resulting additional rework. Fuel pumps, brake boosters, clutch master and slave, etc.

Other possibilities
fuel filter - change it
Multec Injectors - if you still have the original injectors throw in trash and pick up a set of Delphi III injectors. FIC Fuel Injector Connection is on this forum and you can pick up a set of reman and balanced injectors for under $200.

Hope this helps as I've been working on my 1989 for a few years and getting ready to go racing. Check out my build thread for additional details and pictures.

 

Ok so here are a few updates. I went ahead and swapped the fuel pump relay as suggested and it made no difference. Then I went to autozone and went through three fuel pressure gauges before I found one that wasn't defective and here are my results:



Key to on - PSI jumps to 44, then down to 40 after two seconds and slowly back to to 44.
Key to Engine Start - PSI remains at 44.
Key to off - PSI drops to 40 and climbs back up to 44.
Car off for 10 minutes - Pressure drops slowly to around 39.



The entire test can be viewed here (Sorry for the music and focus issues)
https://www.youtube.com/watch?v=QgJO...ature=youtu.be


What should I try next?

 

Fuel pressure is fine, what exactly happens when you try and start the car, in other words what does it sound like? If you could get a video of that it could help us figure it out. Is the computer chip stock for a 1989? I would also look at your engine temperature sensor, the sensor may be reading incorrectly causing the engine to think it is warm when the engine is cold and not adding in enough starting fuel. The best way to do this is with a scanner.