Intermittent crank no start, electrical/fuel related?

Hi,

You may hear the fuel pump, but it may not be producing enough pressure to run the engine. I would recommend checking fuel pressure. You will need a fuel pressure gauge, but most parts stores will lend one to you.

Here is a link that explains in general how it's done:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

The idea that it started with starting fluid indicates it is a fuel-related issue. Keep in mind that the pressure may be good, but we could also have an issue with an injector pulse. But that is something we will check after the pressure is confirmed.

I attached the manufacturer's fuel pressure specifications below. Also, let me know which schematics you will need.

Take care,

Joe

See pic below.

Okay, thank you, I'll try and check fuel pressure this week.
-S.R.

Hi,

Let me know what you find. If the pressure is good, we will need to check for an injector pulse. I'm focused on fuel since it started with starting fluid.

Take care and I look forward to hearing from you.

Joe

Hi Joe,

I am going to test the fuel pressure and replace the fuel filter today. The car probably won't start on its own, would it be okay rig up fuel pressure gauge then get it going with starter fluid to measure fuel pressure at idle? Where are the vacuum lines located? Also, I was wondering if I need to bleed the fuel lines of air after doing this, or if the system priming will do that on its own. Thank you so much.
-S

Hi,

You don't need to start the engine. The fuel pressure with the key on should tell us what we need to know.

As far as bleeding after testing, no need. It will do it by itself. And vacuum lines are in several areas under the hood. Usually, they will be a black rubber-type hose. The inside diameters are commonly between 1/8" and 3/8".

I may have misunderstood you. If you are referring to the vacuum line at the regulator, see pic 1 below. However, with the engine off, that won't make a difference.

Let me know if that helps.

Joe

See pic below.

Okay, thanks so much, I tested fuel pressure today and replaced fuel filter.
Fuel Pressure > I checked fuel pressure inline after the filter and had it jump up to 40/45 when it primes, then start dropping. I tried priming a number of times and pressure continued to jump to 40/45, then fall at a rate of between 0.5-4 psi/ sec. While cranking pressure jumped around 45/50 and stayed there while cranking but truck would not turn over. The truck would not turn over with starter fluid in the intake. Replaced fuel filter and it was still not starting but did not test pressure with new filter.
-FPR - What type of issues will failing fuel pressure regulator cause? It is tucked behind intake manifold and hard to get to, are there ways to test it that don't involve removing manifold? Also - I didn't see any pressure test valves on the fuel rails, are there any on this car?

Camshaft Pos Sensor > After cranking car and not being able to get it to turn over w starting fluid, I checked codes. Had 1 code - PO 0340 Camshaft Position Sensor A (Circuit Bank 1 or Single Sensor). I have had this code come up once before, after crank no starting (due to faulty kill switch) a while ago. I tried cranking while watching RPMs and realized they are at 0, not jumping at all while cranking. Camshaft Pos sensor is in the distributor, 12V constant and ground to Distributor/Camshaft Pos sensor tested good. Would need to do more testing to see if camshaft pos sensor is producing correct signals. Are there any other diagnostics you would do relating to camshaft pos sensor and distributor?

Thanks for taking the time to read,
-S.R.

It sounds like there may be more than one problem. The pressure shouldn't drop that fast. Also, if you have no RPM signal, the crankshaft position sensor is my first suspect. (see pic below) If you have a live data scan tool, check to see if there is an RPM signal when cranking.

Next, you could have an injector or injectors leaking. Remove a few spark plugs to see if they are wet with fuel. The engine may be flooded and not starting if they are leaking.

Let me know.

Joe

Okay, thank you. I'll check live RPM data while cranking. What does it mean if there is/isn't live data? Are there other diagnostics I should go through to check Crankshaft Position Sensor? I'll also try and pull a spark plug to see if it's flooded. Thank you!
-S

I get live RPM data stream while cranking, 0 on dash tachometer. I'm going to pull the cap off the distributor today and see if it looks like any bearings have failed in there.

Hi,

If you have a live signal (RPM), the crankshaft position sensor isn't a likely problem. I know the tachometer is regulated by a signal from the ECM (terminal 3) to terminal 48 of the tachometer.

Let me know if you find any issues with the distributor. Also, let me know if there is spark to the plugs.

Take care,

Joe

Okay, yeah, live RPM signal was good just nothing on tachometer. I opened distributor cap to see if it looks like its dusty or had a failed bearing like I've seen in some YouTube videos. The optical timing disk looked clean and there wasn't too much dust or debris in there. I would like to test the camshaft position sensor more to see if it has the 120-degree REF signal, as well as 1 degree POS signal. I still need to figure out how to turn my crankshaft by hand to test this though. I don't have the right tools to pull my spark plugs at the moment, when I do pull them, I'll check for spark but may not be able to pull all 6. Do you know if the ECM is using multiple sensor inputs to calculate signal to tachometer, if so is one of them the Camshaft Pos Sensor in addition to Crankshaft pos? Thanks so much, and happy New Year!
-S

As far as sensors are concerned, the CKP is what provides the ECM with engine speed. I just double-checked and that is the only thing that is indicated.

Not to sound crazy but have someone crank the engine while you confirm the rotor in the distributor turns.

Let me know.

Joe

Okay, yeah, I can do that. Do you mean open the distributor cap and crank the engine from ignition? Or turn by hand? Thanks so much.

Hi,

Just crank the engine from the key.

Let me know.

Joe

Hello, sorry I was traveling during January and not working on my truck. The distributor rotor is turning. Truck still crank no starting with no dashboard RPM data. Do you have any information about the sensors that provide RPM data to the dashboard VS to live data? I also might check injector pulse with a test light.
Thanks
-S

Hi,

Welcome back. I hope the travel was for fun. LOL

The easiest way to check the crankshaft position sensor is to check if the spark plugs are getting spark.

Here is a link that explains how to do that:

https://www.2carpros.com/articles/how-to-check-for-ignition-spark

Let me know.

Joe